Remove backwards compatible build targets.

Introduced by https://webrtc-review.googlesource.com/c/src/+/224200,
they can be now removed.

Bug: webrtc:11516
Change-Id: Idee5925e1ab10eba1b7b5cf7e673758281ac1492
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/225204
Reviewed-by: Andrey Logvin <landrey@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34440}

sdk/BUILD.gn

@@ -525,21 +525,6 @@ if (is_ios || is_mac) {
       ]
     }
 
-    # For backward compatibility.
-    rtc_source_set("video_objc") {
-      visibility = [ "*" ]
-      public_deps = [ ":opengl_objc" ]  # no-presubmit-check TODO(webrtc:8603)
-    }
-    rtc_source_set("ui_objc") {
-      visibility = [ "*" ]
-      allow_poison = [
-        "audio_codecs",  # TODO(bugs.webrtc.org/8396): Remove.
-        "default_task_queue",
-      ]
-      public_deps =  # no-presubmit-check TODO(webrtc:8603)
-          [ ":opengl_ui_objc" ]
-    }
-
     rtc_library("metal_objc") {
       visibility = [ "*" ]
       allow_poison = [