CI/Flatpak: Disable ffmpeg support

So sick of dealing with fragmented bullshit because different packaging
systems and operating systems have different library versions.

Freedesktop SDK is stuck at ffmpeg 7.0, so it loses support.

scripts/packaging/flatpak/org.duckstation.DuckStation.yaml

@@ -7,12 +7,6 @@ runtime-version: "6.9"
 sdk: "org.kde.Sdk"
 sdk-extensions:
   - "org.freedesktop.Sdk.Extension.llvm19"
-add-extensions:
-  "org.freedesktop.Platform.ffmpeg-full":
-    directory: "lib/ffmpeg"
-    version: "24.08"
-    add-ld-path: "."
-    autodownload: true
 
 command: "duckstation-qt"
 
@@ -95,5 +89,3 @@ modules:
         "${FLATPAK_BUILDER_BUILDDIR}/scripts/packaging/flatpak/org.duckstation.DuckStation.metainfo.xml"
         "${FLATPAK_DEST}/share/metainfo/org.duckstation.DuckStation.metainfo.xml"
 
-      # Ensure ffmpeg-full mount point exists.
-      - "mkdir -p \"${FLATPAK_DEST}/lib/ffmpeg\""