No need to bundle gst-libav in the flatpak any more

756c9f23 "Merge upstream fixes into
solenv/flatpak-manifest.in" had introduced it (via <https://github.com/flathub/
org.libreoffice.LibreOffice/commit/7d69e505165d4bbf5fa0b34b5fb2cbff9dfaf9bd>
"For now, bundle gst-libav to be able to play mp4 videos in impress" to fix
<https://github.com/flathub/org.libreoffice.LibreOffice/issues/20> "Impress
don't insert a video" back when the LO flatpak was based on
org.gnome.Platform//3.26 which doesn't contain
/usr/lib/gstreamer-1.0/libgstlibav.so.  (And
/app/lib/gstreamer-1.0/libgstlibav.so is apparently the only file that the
gst-libav module contributes to the LO flatpak.)

When 727bfa2c "Merge in Flatpak improvements"
switched the runtime to org.freedesktop.Platform//1.6 (via
<https://github.com/flathub/org.libreoffice.LibreOffice/commit/
7a2393f5fcab8c6938180c4718f2c61acd495528> "port to freedesktop.org 1.6 runtime")
it kept the gst-libav module even though org.freedesktop.Platform//1.6 contains
/usr/lib/gstreamer-1.0/libgstlibav.so.  Lets assume it was kept by accident and
can be removed.  (At least the scenario from <https://github.com/flathub/
org.libreoffice.LibreOffice/issues/20#issuecomment-368543622> "Impress don't
insert a video" still works with this change.)

Change-Id: I692d01bfe5882c05d63124db7cdfa6390540e69f
Reviewed-on: https://gerrit.libreoffice.org/64703
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

solenv/flatpak-manifest.in

@@ -31,18 +31,6 @@
                 "/usr/lib/sdk/openjdk10/install.sh"
             ]
         },
-        {
-            "name": "gst-libav",
-            "config-opts": [ "--disable-gtk-doc", "--with-system-libav" ],
-            "cleanup": [ "*.la", "/share/gtk-doc" ],
-            "sources": [
-                {
-                    "type" : "archive",
-                    "url" : "https://gstreamer.freedesktop.org/src/gst-libav/gst-libav-1.10.5.tar.xz",
-                    "sha256" : "e4d2f315f478d47281fbfdfbd590a63d23704ca37911d7142d5992616f4b28d3"
-                }
-            ]
-        },
         {
             "name": "gvfs",
             "cleanup": [ "/libexec/*", "/share/dbus-1/services/*", "/share/gvfs/mounts" ],