FCE-3912 Keep iOS call audio working after audio-session changes and CallKit hold

[Magmusacy]

Description

1. Bumps react-native-webrtc to iOS: keep call audio after audio session changes and CallKit hold fishjam-react-native-webrtc#102: FishjamWebRTC 124.0.2.4 restarts the audio unit when something else stops it, and CallKitManager switches WebRTC audio off while a CallKit call is held.
2. Removes fishjam-chat's held handler, which called stopMicrophone() on hold and startMicrophone() on resume.

Motivation and Context

Fixes iOS call audio going silent after another library deactivates the audio session, or after a CallKit call is held and resumed.

The held handler broke resume on its own: startMicrophone() creates a new track but doesn't publish it, so the other side heard silence after the call was resumed. Hold is now handled natively.

Documentation impact

• Documentation update required
• Documentation updated in another PR
• No documentation update required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)

[linear]

FCE-3912