chore: regenerate README (#1440)

This PR was generated using Autosynth. 🌈


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

```
2021-07-08 20:53:20,676 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-bigquery/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-07-08 20:53:22,072 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/4926a2b2-9b00-4061-9c12-b8f03ce3b96b/targets

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-bigquery.git",
-        "sha": "9d67e05d2a6fab0c9e6017dec33b0d74ad821825"
+        "sha": "3d17e181472b60805a12e446463c13e1788416ec"
       }
     },
     {

README.md

@@ -19,7 +19,7 @@ See https://github.com/GoogleCloudPlatform/cloud-opensource-java/wiki/The-Google
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>20.7.0</version>
+      <version>20.8.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -53,12 +53,12 @@ compile 'com.google.cloud:google-cloud-bigquery'
 ```
 If you are using Gradle without BOM, add this to your dependencies
 ```Groovy
-compile 'com.google.cloud:google-cloud-bigquery:1.135.4'
+compile 'com.google.cloud:google-cloud-bigquery:1.136.0'
 ```
 
 If you are using SBT, add this to your dependencies
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-bigquery" % "1.135.4"
+libraryDependencies += "com.google.cloud" % "google-cloud-bigquery" % "1.136.0"
 ```
 
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