Revert "Add ios bindings for PeerConnectionState."

This reverts commit 586725dc9a508c7d3e82b5a625a5ee7e8b1a4e17.

Reason for revert: misses a check to see if the optional callback is implemented.

Original change's description:
> Add ios bindings for PeerConnectionState.
> 
> This change makes it possible for ios apps to use the new standards-compliant PeerConnectionState.
> 
> Bug: webrtc:9977
> Change-Id: Icf69bb1faa0383ae239cb7508f2a740a2d489697
> Reviewed-on: https://webrtc-review.googlesource.com/c/110502
> Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
> Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25651}

TBR=kthelgason@webrtc.org,jonasolsson@webrtc.org

Change-Id: Iff919e9876e6b8dddc6d8ab7df302081d0cfa917
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9977
Reviewed-on: https://webrtc-review.googlesource.com/c/111062
Reviewed-by: Jonas Olsson <jonasolsson@webrtc.org>
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25659}

examples/objc/AppRTCMobile/ARDAppClient.m

@@ -404,11 +404,6 @@ static int const kKbpsMultiplier = 1000;
   });
 }
 
-- (void)peerConnection:(RTCPeerConnection *)peerConnection
-    didChangeConnectionState:(RTCPeerConnectionState)newState {
-  RTCLog(@"ICE+DTLS state changed: %ld", (long)newState);
-}
-
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     didChangeIceGatheringState:(RTCIceGatheringState)newState {
   RTCLog(@"ICE gathering state changed: %ld", (long)newState);