[Chromecast] Remove libffmpegsumo dummy

BUG=internal b/21639416

Review URL: https://codereview.chromium.org/1473003002

Cr-Commit-Position: refs/heads/master@{#361220}

chromecast/media/BUILD.gn

@@ -58,9 +58,3 @@ test("cast_media_unittests") {
     "//ui/gfx/geometry",
   ]
 }
-
-# TODO(slan): delete this target once Chromecast M44/earlier is obsolete.
-# See: b/21639416
-shared_library("libffmpegsumo") {
-  output_name = "libffmpegsumo"
-}

chromecast/media/media.gyp

@@ -14,13 +14,6 @@
     ],
   },
   'targets': [
-    # TODO(slan): delete this target once Chromecast M44/earlier is obsolete.
-    # See: b/21639416
-    {
-      'target_name': 'libffmpegsumo',
-      'type': 'loadable_module',
-      'sources': ['empty.cc'],
-    },
     {
       'target_name': 'media_audio',
       'type': '<(component)',