Bump com.google.code.gson:gson from 2.8.6 to 2.8.9

Bumps [com.google.code.gson:gson](https://github.com/google/gson) from 2.8.6 to 2.8.9.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/main/CHANGELOG.md)
- [Commits](google/gson@gson-parent-2.8.6...gson-parent-2.8.9)

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

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

Author: dependabot[bot]

Diff for: buildSrc/build.gradle

@@ -75,7 +75,7 @@ configurations {
 }
 
 dependencies {
-    implementation 'com.google.code.gson:gson:2.8.6'
+    implementation 'com.google.code.gson:gson:2.8.9'
     implementation 'com.thaiopensource:trang:20091111'
     implementation 'net.sourceforge.saxon:saxon:9.1.0.8'
     implementation 'org.yaml:snakeyaml:1.30'