[webcodecs] Remove the redundant namespace denotation.

Bug: None
Change-Id: I961d82b32465546f935fcec5047b005fdec370a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2513352Reviewed-by: Eugene Zemtsov <eugene@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Chunbo Hua <chunbo.hua@intel.com>
Cr-Commit-Position: refs/heads/master@{#823927}

media/formats/mp4/h264_annex_b_to_avc_bitstream_converter.cc

@@ -204,6 +204,6 @@ Status H264AnnexBToAvcBitstreamConverter::ConvertChunk(
     *config_changed_out = config_changed;
 
   return Status();
-}  // namespace media
+}
 
 }  // namespace media
\ No newline at end of file