Removing gstreamer git master from gnome-build-meta

[Abderrahim Kitouni <akitouni gnome org>]

Hi all,

We would like to remove gstreamer master from gnome-build-meta. What
this means is that the nightly flatpak runtimes will have the latest
gstreamer stable version (1.14.4 as of this writing, but 1.16 should
be released soon).

I believe this won't break anything, but if you think you really need
gstreamer master, please speak up in this issue:
https://gitlab.gnome.org/GNOME/gnome-build-meta/issues/97

Cheers,

Abderrahim