chore(deps): bump gson from 2.2.2-atlassian-1 to 2.8.9 in /plugin

Bumps [gson](https://github.com/google/gson) from 2.2.2-atlassian-1 to 2.8.9.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/gson/commits/gson-parent-2.8.9)

---
updated-dependencies:
- dependency-name: com.google.code.gson:gson
  dependency-type: direct:production
...

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

Author: dependabot[bot]

plugin/pom.xml

@@ -79,7 +79,7 @@
         <dependency>
             <groupId>com.google.code.gson</groupId>
             <artifactId>gson</artifactId>
-            <version>2.2.2-atlassian-1</version>
+            <version>2.8.9</version>
         </dependency>
 
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