Fix generated docs check errors.

Author: nakirekommula

gma/src/include/firebase/gma/types.h

@@ -153,14 +153,23 @@ enum AdErrorCode {
   kAdErrorCodeUnknown,
 };
 
+#if !defined(DOXYGEN)
+/// Format of the ad being requested. Currently used only for internal updates.
 enum AdFormat {
+  /// App open ad format.
   kAdFormatAppOpen,
+  /// Banner ad format.
   kAdFormatBanner,
+  /// Interstitial ad format.
   kAdFormatInterstitial,
+  /// Native ad format.
   kAdFormatNative,
+  /// Rewarded ad format.
   kAdFormatRewarded,
+  /// Rewarded interstitial ad format.
   kAdFormatRewardedInterstitial,
 };
+#endif  // !defined(DOXYGEN)
 
 /// A listener for receiving notifications during the lifecycle of a BannerAd.
 class AdListener {