bump mapbox-java to 6.8.0 (#6413)

Author: Zayankovsky

gradle/dependencies.gradle

@@ -19,7 +19,7 @@ ext {
 
   version = [
       mapboxMapSdk              : '10.8.0',
-      mapboxSdkServices         : '6.8.0-beta.4',
+      mapboxSdkServices         : '6.8.0',
       mapboxEvents              : '8.1.5',
       mapboxCore                : '5.0.2',
       mapboxNavigator           : "${mapboxNavigatorVersion}",