[FEATURE] Support AgoraRtcEngine_iOS ~> 4.3.0

[dgimb89]

Is your feature request related to a problem? Please describe.
We're experiencing some audio recording issues in Agora video calls that have since been fixed in the new AgoraRtcEngine 4.3 release. Unfortunately the AgoraBroadcastExtensionHelper_iOS pod is pinned to ~> 4.2.0, which prevents us from upgrading.

Describe the solution you'd like
Relax version constraint to 4.3:
s.dependency 'AgoraRtcEngine_iOS', '~> 4.3.0'
We've relaxing the implementation locally, and it worked fine without any issues during testing.

Describe alternatives you've considered
We could fork this repo and relax it ourselves. This is not our preferred option.

Additional context

target 'RecordingExtension' do
  use_frameworks!

  pod 'AgoraRtcEngine_iOS', '4.3.2'
  pod 'AgoraBroadcastExtensionHelper_iOS', '4.1.1'
end