Bump gson from 2.8.9 to 2.9.0

Bumps [gson](https://github.com/google/gson) from 2.8.9 to 2.9.0.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/gson/compare/gson-parent-2.8.9...gson-parent-2.9.0)

---
updated-dependencies:
- dependency-name: com.google.code.gson:gson
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

build.gradle

@@ -121,7 +121,7 @@ allprojects  {
 
             dependency 'org.apache.openjpa:openjpa:3.2.0' // when upgrading, also change OpenJPA version repeated above in buildscript!
             dependency 'com.google.guava:guava:31.0.1-jre'
-            dependency 'com.google.code.gson:gson:2.8.9'
+            dependency 'com.google.code.gson:gson:2.9.0'
             dependency 'com.google.truth:truth:1.1.3'
             dependency 'com.google.truth.extensions:truth-java8-extension:1.1.3'
             dependency 'org.apache.commons:commons-email:1.5'