gst_all_1.gst-libav: remove ffmpeg pin

GStreamer 1.28.6 adds support for ffmpeg 9.

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

@@ -9,8 +9,7 @@
   gstreamer,
   gst-plugins-base,
   gettext,
-  # FIXME: unpin when upstream supports ffmpeg 9
-  ffmpeg_8-headless,
+  ffmpeg-headless,
   # Checks meson.is_cross_build(), so even canExecute isn't enough.
   enableDocumentation ? stdenv.hostPlatform == stdenv.buildPlatform,
   hotdoc,
@@ -51,7 +50,7 @@ stdenv.mkDerivation (finalAttrs: {
   buildInputs = [
     gstreamer
     gst-plugins-base
-    ffmpeg_8-headless
+    ffmpeg-headless
   ]
   ++ lib.optionals stdenv.hostPlatform.isDarwin [
     apple-sdk_gstreamer