Update dependency com.google.code.gson:gson to v2.8.5 (#657)

Author: renovate-bot

pom.xml

@@ -545,7 +545,7 @@
     <project.appengine.version>1.9.71</project.appengine.version>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.jsr305.version>3.0.2</project.jsr305.version>
-    <project.gson.version>2.1</project.gson.version>
+    <project.gson.version>2.8.5</project.gson.version>
     <project.jackson-core2.version>2.9.9</project.jackson-core2.version>
     <project.protobuf-java.version>3.6.1</project.protobuf-java.version>
     <project.guava.version>26.0-android</project.guava.version>