Bump gson from 2.8.5 to 2.8.9

Bumps [gson](https://github.com/google/gson) from 2.8.5 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-2.8.5...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>

Author: dependabot[bot]

pom.xml

@@ -43,7 +43,7 @@
         <scala.version>2.11.12</scala.version>
         <jdk.compile.version>1.8</jdk.compile.version>
         <maven.version>3.3.3</maven.version>
-        <gson.version>2.8.5</gson.version>
+        <gson.version>2.8.9</gson.version>
         <fasterxml.jackson.version>2.12.6.1</fasterxml.jackson.version>
         <org.codehaus.jackson.version>1.9.13</org.codehaus.jackson.version>
         <math3.version>3.1.1</math3.version>