deps: update gax.version to v1.64.0 (#345)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.api:gax-grpc](https://github.com/googleapis/gax-java) | `1.63.0` -> `1.64.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/1.64.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/1.64.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/1.64.0/compatibility-slim/1.63.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/1.64.0/confidence-slim/1.63.0)](https://docs.renovatebot.com/merge-confidence/) |
| [com.google.api:gax-bom](https://github.com/googleapis/gax-java) | `1.63.0` -> `1.64.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/1.64.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/1.64.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/1.64.0/compatibility-slim/1.63.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/1.64.0/confidence-slim/1.63.0)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

<details>
<summary>googleapis/gax-java</summary>

### [`v1.64.0`](https://github.com/googleapis/gax-java/blob/master/CHANGELOG.md#&#8203;1640-httpswwwgithubcomgoogleapisgax-javacomparev1634v1640-2021-05-10)

[Compare Source](https://github.com/googleapis/gax-java/compare/v1.63.4...v1.64.0)

##### Features

-   release 1.64.0 ([#&#8203;1375](https://www.github.com/googleapis/gax-java/issues/1375)) ([499682e](https://www.github.com/googleapis/gax-java/commit/499682ec3b96ddeaac75f6e71cc3bc85a854da97))

##### [1.63.4](https://www.github.com/googleapis/gax-java/compare/v1.63.3...v1.63.4) (2021-05-07)

##### Bug Fixes

-   Make x-goog-api-client header report rest-based transport clients with `rest/` token instead of `httpson/`. ([#&#8203;1370](https://www.github.com/googleapis/gax-java/issues/1370)) ([b1b0b49](https://www.github.com/googleapis/gax-java/commit/b1b0b498ba188a51b17d179988074bcf34fb7590))

##### [1.63.3](https://www.github.com/googleapis/gax-java/compare/v1.63.2...v1.63.3) (2021-05-04)

##### Bug Fixes

-   fix flaky tests and non blocking semaphore ([#&#8203;1365](https://www.github.com/googleapis/gax-java/issues/1365)) ([fc8e520](https://www.github.com/googleapis/gax-java/commit/fc8e520acfaf843ac61e806bdb4b5fe393d0b447))
-   Remove a flacky test in FlowControllerTest ([#&#8203;1360](https://www.github.com/googleapis/gax-java/issues/1360)) ([2cca0bf](https://www.github.com/googleapis/gax-java/commit/2cca0bf9e96271dd52e8bffa00b8f2d45d358d35))

##### [1.63.2](https://www.github.com/googleapis/gax-java/compare/v1.63.1...v1.63.2) (2021-04-30)

##### Bug Fixes

-   Remove default value handling ([#&#8203;1353](https://www.github.com/googleapis/gax-java/issues/1353)) ([ed0fc79](https://www.github.com/googleapis/gax-java/commit/ed0fc791b22db45bd20de890b0abecd1839d2d86))

##### Dependencies

-   remove codecov.io ([#&#8203;1354](https://www.github.com/googleapis/gax-java/issues/1354)) ([06a53ac](https://www.github.com/googleapis/gax-java/commit/06a53aca36ed0825122be160479b1ea0ba8635a0))

##### [1.63.1](https://www.github.com/googleapis/gax-java/compare/v1.63.0...v1.63.1) (2021-04-26)

##### Bug Fixes

-   fix dynamic flow control setting checks ([#&#8203;1347](https://www.github.com/googleapis/gax-java/issues/1347)) ([69458b4](https://www.github.com/googleapis/gax-java/commit/69458b4deefe5b9c2c33a3b51389face968ff52f))
-   fix watchdog NPE red herring ([#&#8203;1344](https://www.github.com/googleapis/gax-java/issues/1344)) ([06dbf12](https://www.github.com/googleapis/gax-java/commit/06dbf129ce63d28430e1022137679c9cfdf433ee))

### [`v1.63.4`](https://github.com/googleapis/gax-java/blob/master/CHANGELOG.md#&#8203;1634-httpswwwgithubcomgoogleapisgax-javacomparev1633v1634-2021-05-07)

[Compare Source](https://github.com/googleapis/gax-java/compare/v1.63.3...v1.63.4)

### [`v1.63.3`](https://github.com/googleapis/gax-java/blob/master/CHANGELOG.md#&#8203;1633-httpswwwgithubcomgoogleapisgax-javacomparev1632v1633-2021-05-04)

[Compare Source](https://github.com/googleapis/gax-java/compare/v1.63.0...v1.63.3)

</details>

---

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pom.xml

@@ -56,7 +56,7 @@
     <site.installationModule>${project.artifactId}</site.installationModule>
 
     <grpc.version>1.37.0</grpc.version>
-    <gax.version>1.63.0</gax.version>
+    <gax.version>1.64.0</gax.version>
     <guava.version>30.1.1-android</guava.version>
     <protobuf.version>3.16.0</protobuf.version>
     <google.api-common.version>1.10.3</google.api-common.version>