gst-plugins-bad: remove xvidcore dependency

Removed upstream in 9b5de053995488d5ddc78c1bf4df651101271d70 [1].
Took effect in release 1.11.1 released Jan 2017 [2].

[1] https://github.com/GStreamer/gst-plugins-bad/commit/9b5de053995488d5ddc78c1bf4df651101271d70
[2] https://github.com/GStreamer/gst-plugins-bad/releases/tag/1.11.1

pkgs/development/libraries/gstreamer/bad/default.nix

@@ -80,7 +80,6 @@
 , libva
 , wayland
 , libwebp
-, xvidcore
 , gnutls
 , mjpegtools
 , libGL
@@ -196,7 +195,6 @@ stdenv.mkDerivation (finalAttrs: {
     srtp
     fluidsynth
     libwebp
-    xvidcore
     gnutls
     game-music-emu
     openssl