Remove warning suppression from VideoToolboxEncoder

This warning no longer needs to be supressed as the issue
has been fixed.

BUG=webrtc:6307
TBR=tkchin@webrtc.org

Review-Url: https://codereview.webrtc.org/2537293003
Cr-Commit-Position: refs/heads/master@{#15331}
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index 625c28f..7d2036b 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -30,14 +30,6 @@
       "objc/Framework/Headers",
     ]
   }
-  config("webrtc_h264_video_toolbox_warnings_config") {
-    if (is_clang) {
-      # TODO(tkchin): Make webrtc_h264_video_toolbox compile with the standard set
-      # of warnings.
-      # See https://bugs.chromium.org/p/webrtc/issues/detail?id=6307
-      cflags = [ "-Wno-thread-safety-analysis" ]
-    }
-  }
 
   rtc_static_library("rtc_sdk_common_objc") {
     deps = [
@@ -385,7 +377,6 @@
     ]
 
     configs += [
-      ":webrtc_h264_video_toolbox_warnings_config",
       "//webrtc:common_objc",
       "//build/config/compiler:enable_arc",
     ]