Update build.gradle

rollback to gson v2.9.1 due to a crash when loading GLTF model

Author: scenemax3d

jme3-plugins-json-gson/build.gradle

@@ -11,6 +11,6 @@ sourceSets {
 dependencies {
 
     api project(':jme3-plugins-json')
-    api 'com.google.code.gson:gson:2.10.1'
+    api 'com.google.code.gson:gson:2.9.1'
 
 }