Cast listener with __block

[qdpham13]

Cast Listener with __block so changes can be made inside dispatch_async block.
Fixes bug reported by user

[google-oss-bot]

	1 Warning
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[google-oss-bot]

Coverage Report ¹

Affected Products

• FirebaseRemoteConfig-iOS-FirebaseRemoteConfig.framework

  Overall coverage changed from 71.00% (3f5972f) to 71.01% (60b4cf2) by +0.01%.

  Filename	Base (3f5972f)	Merge (60b4cf2)	Diff
  RCNConfigRealtime.m	35.85%	35.93%	+0.08%

Test Logs

• Base (3f5972f): https://github.com/firebase/firebase-ios-sdk/actions/runs/5324914869
• Merge (60b4cf2): https://github.com/firebase/firebase-ios-sdk/actions/runs/5327702235

1. https://storage.googleapis.com/firebase-sdk-metric-reports/HTl7mODq6T.html

[mikehardy]

Fantastic, thanks @qdpham13 - I was able to view the raw file from your tree, paste that into my build in place of my current file contents and re-test my scenario.

Previously, since the listeners were not removed from the SDK they would accumulate, and at the javascript layer of react-native-firebase we would see the clear symptom of more events than we expected (specifically: we would see one extra event for each add/remove cycle we did as we probed the APIS and our implementation)

With your change, I no longer see an incremental accumulation of extra callback events, indicating that the listeners are now being removed inside the SDK --> so this appears to work 👍

[mikehardy]

weak objective-c skills and zero authority in this repo :-) but I did test it, appears to work