[gimp] flatpak: Use exact version of GEGL (0.4.30)

[Jehan <jehanp src gnome org>]

commit 61389adfa02bf799c04c945220772e898df91d65
Author: Ondřej Míchal <harrymichal seznam cz>
Date:   Sun May 23 19:50:58 2021 +0200

    flatpak: Use exact version of GEGL (0.4.30)
    
    Latest git version fails to build.

 build/flatpak/org.gimp.GIMP-nightly.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build/flatpak/org.gimp.GIMP-nightly.json b/build/flatpak/org.gimp.GIMP-nightly.json
index fd9db8e263..6146fb8d93 100644
--- a/build/flatpak/org.gimp.GIMP-nightly.json
+++ b/build/flatpak/org.gimp.GIMP-nightly.json
@@ -438,7 +438,7 @@
                 {
                     "type": "git",
                     "url": "https://gitlab.gnome.org/GNOME/gegl.git";,
-                    "branch": "master"
+                    "tag": "GEGL_0_4_30"
                 }
             ],
             "modules": [