Don't automatically check for FFmpeg updates

Sadly, FFmpeg 4.4 regresses on the nvenc front. We want to hold it
back until it's fixed.

Remove the automatic update check from FFmpeg.

com.obsproject.Studio.json

@@ -173,12 +173,7 @@
                 {
                     "type": "archive",
                     "url": "https://www.ffmpeg.org/releases/ffmpeg-4.4.tar.xz",
-                    "sha256": "06b10a183ce5371f915c6bb15b7b1fffbe046e8275099c96affc29e17645d909",
-                    "x-checker-data": {
-                        "type": "anitya",
-                        "project-id": 5405,
-                        "url-template": "https://www.ffmpeg.org/releases/ffmpeg-$version.tar.xz"
-                    }
+                    "sha256": "06b10a183ce5371f915c6bb15b7b1fffbe046e8275099c96affc29e17645d909"
                 }
             ]
         },