Bump com.pubnub:pubnub-gson from 4.31.3 to 6.4.0

Bumps [com.pubnub:pubnub-gson](https://github.com/pubnub/java) from 4.31.3 to 6.4.0.
- [Release notes](https://github.com/pubnub/java/releases)
- [Changelog](https://github.com/pubnub/java/blob/master/CHANGELOG.md)
- [Commits](pubnub/java@v4.31.3...v6.4.0)

---
updated-dependencies:
- dependency-name: com.pubnub:pubnub-gson
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

pom.xml

@@ -349,7 +349,7 @@
       <dependency>
         <groupId>com.pubnub</groupId>
         <artifactId>pubnub-gson</artifactId>
-        <version>4.31.3</version>
+        <version>6.4.0</version>
       </dependency>
         <!-- Netty version compatible with service-wamp -->
         <dependency>