Bump gson from 2.2.2 to 2.8.9 in /tajo-project

Bumps [gson](https://github.com/google/gson) from 2.2.2 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/compare/gson-2.2.2...gson-parent-2.8.9)

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

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/tajo-project/pom.xml b/tajo-project/pom.xml
index 59628a9..1b885ba 100644
--- a/tajo-project/pom.xml
+++ b/tajo-project/pom.xml
@@ -835,7 +835,7 @@
       <dependency>
         <groupId>com.google.code.gson</groupId>
         <artifactId>gson</artifactId>
-        <version>2.2.2</version>
+        <version>2.8.9</version>
       </dependency>
       <dependency>
         <groupId>org.mockito</groupId>