Remove RTCUIApplicationStatusObserver.

This component was added to work around an issue in iOS 8, which is
no longer supported by WebRTC. It's removal is made more urgent by
the fact that it prevents WebRTC being used by iOS extensions.

Bug: webrtc:9335
Change-Id: I2a3327534fe6d5014c34a9e908096d825e8149e3
Reviewed-on: https://webrtc-review.googlesource.com/87822
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24688}

sdk/objc/components/video_codec/RTCVideoDecoderH264.mm

@@ -76,13 +76,6 @@ void decompressionOutputCallback(void *decoderRef,
   OSStatus _error;
 }
 
-- (instancetype)init {
-  if (self = [super init]) {
-  }
-
-  return self;
-}
-
 - (void)dealloc {
   [self destroyDecompressionSession];
   [self setVideoFormat:nullptr];