[gnome-builder] meson-templates: use fallback-x11 in flatpak

[Christian Hergert <chergert src gnome org>]

commit b1645c8d77a6241621dc90226435a4e4d0d4ece7
Author: Mohammed Sadiq <sadiq sadiqpk org>
Date:   Sun Aug 4 22:47:02 2019 +0530

    meson-templates: use fallback-x11 in flatpak
    
    This was introduced in flatpak version 0.11.1 to allow X11 acess only
    if running in an X11 session.

 src/plugins/meson-templates/resources/flatpak.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/plugins/meson-templates/resources/flatpak.json 
b/src/plugins/meson-templates/resources/flatpak.json
index ff88562e3..e16a4ccda 100644
--- a/src/plugins/meson-templates/resources/flatpak.json
+++ b/src/plugins/meson-templates/resources/flatpak.json
@@ -7,7 +7,7 @@
     "finish-args": [
         "--share=network",
         "--share=ipc",
-        "--socket=x11",
+        "--socket=fallback-x11",
         "--socket=wayland",
         "--filesystem=xdg-run/dconf",
         "--filesystem=~/.config/dconf:ro",