Revert "updating gson to 2.10 to support gson.Strictness (#32)" (#33)

This reverts commit 5fa63fb.

Author: sagar-zendesk

jazon-core/build.gradle

@@ -6,7 +6,7 @@ ext {
 apply from: '../gradle/publishing.gradle'
 
 dependencies {
-    compile group: 'com.google.code.gson', name: 'gson', version: '2.10'
+    compile group: 'com.google.code.gson', name: 'gson', version: '2.9.1'
 
     compileOnly 'org.projectlombok:lombok:1.18.12'
     annotationProcessor 'org.projectlombok:lombok:1.18.12'