Bump gson from 2.8.7 to 2.8.9

Bumps [gson](https://github.com/google/gson) from 2.8.7 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-2.8.7...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

@@ -56,7 +56,7 @@
         <jacksonVersion>2.10.1</jacksonVersion>
         <apacheHttpClientVersion>4.5.10</apacheHttpClientVersion>
         <itextPdfVersion>7.1.13</itextPdfVersion>
-        <gsonVersion>2.8.7</gsonVersion>
+        <gsonVersion>2.8.9</gsonVersion>
         <apacheCommonsVersion>1.3</apacheCommonsVersion>
 
     </properties>