[nautilus] Flatpak: Use 3.28 version

[Carlos Soriano <csoriano src gnome org>]

commit e212a3f703287bee47e8ebfcdfde73e27c461fcb
Author: Carlos Soriano <csoriano redhat com>
Date:   Thu May 17 16:35:04 2018 +0200

    Flatpak: Use 3.28 version
    
    Until master is fixed, due to the rebase to fdo 1.8.

 build-aux/flatpak/org.gnome.Nautilus.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Nautilus.json b/build-aux/flatpak/org.gnome.Nautilus.json
index b97a03bb0..4073ea96e 100644
--- a/build-aux/flatpak/org.gnome.Nautilus.json
+++ b/build-aux/flatpak/org.gnome.Nautilus.json
@@ -1,7 +1,7 @@
 {
     "app-id": "org.gnome.NautilusDevel",
     "runtime": "org.gnome.Platform",
-    "runtime-version": "master",
+    "runtime-version": "3.28",
     "sdk": "org.gnome.Sdk",
     "command": "nautilus",
     "tags": ["devel", "development", "nightly"],