deps: update gax.version to v2.3.0 (#437)

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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) | `2.1.0` -> `2.3.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/2.3.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/2.3.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/2.3.0/compatibility-slim/2.1.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.api:gax-grpc/2.3.0/confidence-slim/2.1.0)](https://docs.renovatebot.com/merge-confidence/) |
| [com.google.api:gax-bom](https://github.com/googleapis/gax-java) | `2.1.0` -> `2.3.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/2.3.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/2.3.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/2.3.0/compatibility-slim/2.1.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.api:gax-bom/2.3.0/confidence-slim/2.1.0)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v2.3.0`](https://github.com/googleapis/gax-java/blob/master/CHANGELOG.md#&#8203;230-httpswwwgithubcomgoogleapisgax-javacomparev220v230-2021-08-16)

[Compare Source](https://github.com/googleapis/gax-java/compare/v2.2.0...v2.3.0)

##### Features

-   add custom options to ApiCallContext ([#&#8203;1435](https://www.github.com/googleapis/gax-java/issues/1435)) ([0fe20f3](https://www.github.com/googleapis/gax-java/commit/0fe20f379feba1570e562e60e3f0bf7cc4e485bd))
-   add UseJwtAccessWithScope to GoogleCredentialsProvider ([#&#8203;1420](https://www.github.com/googleapis/gax-java/issues/1420)) ([ed39c34](https://www.github.com/googleapis/gax-java/commit/ed39c34693783460fc03effb47e7027914cfb5bc))

### [`v2.2.0`](https://github.com/googleapis/gax-java/blob/master/CHANGELOG.md#&#8203;220-httpswwwgithubcomgoogleapisgax-javacomparev210v220-2021-08-13)

[Compare Source](https://github.com/googleapis/gax-java/compare/v2.1.0...v2.2.0)

##### Features

-   Add AIP-151 LRO OperationsClient to gax-httpjson ([#&#8203;1458](https://www.github.com/googleapis/gax-java/issues/1458)) ([314acb6](https://www.github.com/googleapis/gax-java/commit/314acb6a5c335732e8406bec86f6c37296ebf3f3))

</details>

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pom.xml

@@ -54,9 +54,8 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <site.installationModule>${project.artifactId}</site.installationModule>
-
     <grpc.version>1.40.0</grpc.version>
-    <gax.version>2.1.0</gax.version>
+    <gax.version>2.3.0</gax.version>
     <grpc-gcp.version>1.1.0</grpc-gcp.version>
     <guava.version>30.1.1-jre</guava.version>
     <protobuf.version>3.17.3</protobuf.version>