Update capabilities-ios.md

Author: allchiang-msft

articles/communication-services/how-tos/calling-sdk/includes/capabilities/capabilities-ios.md

@@ -58,3 +58,4 @@ public class CapabilitiesCallDelegate : CapabilitiesCallFeatureDelegate
 - *CustomBackground*: Ability to apply a custom background
 - *StartLiveCaptions*: Ability to start live captions
 - *RaiseHand*: Ability to raise hand
+- *MuteOthers*: Ability to soft mute remote participant(s) in the meeting