Bump gson from 2.8.7 to 2.8.8

Bumps [gson](https://github.com/google/gson) from 2.8.7 to 2.8.8.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](google/gson@gson-parent-2.8.7...gson-parent-2.8.8)

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

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

Author: dependabot[bot]

extractor/build.gradle

@@ -16,5 +16,5 @@ dependencies {
 
     testImplementation "junit:junit:$junitVersion"
     testImplementation "com.squareup.okhttp3:okhttp:3.12.13"
-    testImplementation 'com.google.code.gson:gson:2.8.7'
+    testImplementation 'com.google.code.gson:gson:2.8.8'
 }