[gnome-build-meta] flatpak/platform.bst: add forgotten version

[Abderrahim Kitouni <akitouni src gnome org>]

commit c56ce18061741820c72e4cf1cf13646d158e3a81
Author: Abderrahim Kitouni <akitouni gnome org>
Date:   Wed Sep 18 00:28:43 2019 +0100

    flatpak/platform.bst: add forgotten version
    
    Fixes #204

 elements/flatpak/platform.bst | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/elements/flatpak/platform.bst b/elements/flatpak/platform.bst
index 589bc8a6..2892812a 100644
--- a/elements/flatpak/platform.bst
+++ b/elements/flatpak/platform.bst
@@ -83,3 +83,4 @@ config:
       directory: '%{lib}/openh264'
       add-ld-path: extra
       autodelete: 'false'
+      version: '%{freedesktop-sdk-flatpak-branch}'