chore: regenerate README (#679)

This PR was generated using Autosynth. 🌈


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

```
2021-08-27 16:44:55,508 synthtool [DEBUG] > Executing /root/.cache/synthtool/java-dialogflow/.github/readme/synth.py.
On branch autosynth-readme
nothing to commit, working tree clean
2021-08-27 16:44:56,548 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/2b62b131-5349-4e78-a6bb-68d411b1e986/targets

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Author: yoshi-automation

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

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-dialogflow.git",
-        "sha": "ab733c601042c60d55e31290c4e049b44d584798"
+        "sha": "4b09ff255a133c28353ae1a309b389086132daf0"
       }
     },
     {

README.md

@@ -19,7 +19,7 @@ If you are using Maven with [BOM][libraries-bom], add this to your pom.xml file
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>libraries-bom</artifactId>
-      <version>21.0.0</version>
+      <version>22.0.0</version>
       <type>pom</type>
       <scope>import</scope>
     </dependency>
@@ -49,7 +49,7 @@ If you are using Maven without BOM, add this to your dependencies:
 If you are using Gradle 5.x or later, add this to your dependencies
 
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:21.0.0')
+implementation platform('com.google.cloud:libraries-bom:22.0.0')
 
 compile 'com.google.cloud:google-cloud-dialogflow'
 ```