Bump gson from 2.8.0 to 2.8.9 in /redisjson (#47)

Bumps [gson](https://github.com/google/gson) from 2.8.0 to 2.8.9.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/master/CHANGELOG.md)
- [Commits](google/gson@gson-parent-2.8.0...gson-parent-2.8.9)

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

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Author: dependabot[bot]

redisjson/pom.xml

@@ -13,7 +13,7 @@
     <name>RedisJSON</name>
 
     <properties>
-        <gson.version>2.8.0</gson.version>
+        <gson.version>2.8.9</gson.version>
     </properties>
 
     <dependencies>