[android] annotate Mapbox class with @UiThread to make clear that it is required to be started from the main thread as it loads the native library for connectivity change events (#9309)

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/Mapbox.java

@@ -24,6 +24,7 @@ import com.mapbox.services.android.telemetry.location.LocationEnginePriority;
  * connectivity state.
  * </p>
  */
+@UiThread
 public final class Mapbox {
 
   private static Mapbox INSTANCE;