Convert some asserts to FIREBASE_ASSERTs in admob

Some compilers are complaining about unused variables because of how assert works, so swap those to FIREBASE_ASSERT

PiperOrigin-RevId: 282464729

Author: a-maurice

admob/src/android/banner_view_internal_android.cc

@@ -187,7 +187,7 @@ BoundingBox BannerViewInternalAndroid::GetBoundingBox() const {
   // The bounding box array must consist of 4 integers: width, height,
   // x-coordinate, and y-coordinate.
   int count = static_cast<int>(env->GetArrayLength(jni_int_array));
-  assert(count == 4);
+  FIREBASE_ASSERT(count == 4);
 
   jint* bounding_box_elements =
       env->GetIntArrayElements(jni_int_array, nullptr);

admob/src/android/native_express_ad_view_internal_android.cc

@@ -197,7 +197,7 @@ BoundingBox NativeExpressAdViewInternalAndroid::GetBoundingBox() const {
   // The bounding box array must consist of 4 integers: width, height,
   // x-coordinate, and y-coordinate.
   int count = static_cast<int>(env->GetArrayLength(jni_int_array));
-  assert(count == 4);
+  FIREBASE_ASSERT(count == 4);
 
   jint* bounding_box_elements =
       env->GetIntArrayElements(jni_int_array, nullptr);