chore: regenerate README (#681)

This PR was generated using Autosynth. 🌈


<details><summary>Log from Synthtool</summary>

```
2020-11-16 18:45:56,025 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigquerystorage/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working directory clean
2020-11-16 18:45:57,002 synthtool [DEBUG] > Wrote metadata to .github/readme/synth.metadata/synth.metadata.

```
</details>

Full log will be available here:
https://source.cloud.google.com/results/invocations/a850c64f-6318-4d3e-a0c1-9c92a0a9278a/targets

- [ ] To automatically regenerate this PR, check this box.

.github/readme/synth.metadata/synth.metadata

@@ -4,14 +4,14 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigquerystorage.git",
-        "sha": "f0f3f22956aa90a3d06805a4234e1eabab0550ee"
+        "sha": "2d3738da7311efb0ea8a56ba0074c70bbb057b0e"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "e89175cf074dccc4babb4eca66ae913696e47a71"
+        "sha": "d5fc0bcf9ea9789c5b0e3154a9e3b29e5cea6116"
       }
     }
   ]

README.md

@@ -38,18 +38,18 @@ If you are using Maven without BOM, add this to your dependencies:
 <dependency>
   <groupId>com.google.cloud</groupId>
   <artifactId>google-cloud-bigquerystorage</artifactId>
-  <version>1.6.3</version>
+  <version>1.6.4</version>
 </dependency>
 
 ```
 
 If you are using Gradle, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-bigquerystorage:1.6.3'
+compile 'com.google.cloud:google-cloud-bigquerystorage:1.6.4'
 ```
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-bigquerystorage" % "1.6.3"
+libraryDependencies += "com.google.cloud" % "google-cloud-bigquerystorage" % "1.6.4"
 ```
 
 ## Authentication