[gnome-builder] meson-templates: use GNOME 40 SDK

[Christian Hergert <chergert src gnome org>]

commit 1b935467586f2231ba550d960e00e38a4999df68
Author: Christian Hergert <chergert redhat com>
Date:   Wed Mar 24 13:09:47 2021 -0700

    meson-templates: use GNOME 40 SDK

 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 da7f3a265..9574c9e09 100644
--- a/src/plugins/meson-templates/resources/flatpak.json
+++ b/src/plugins/meson-templates/resources/flatpak.json
@@ -1,7 +1,7 @@
 {
     "app-id" : "{{appid}}",
     "runtime" : "org.gnome.Platform",
-    "runtime-version" : "master",
+    "runtime-version" : "40",
     "sdk" : "org.gnome.Sdk",
 {{if language == "rust"}}
     "sdk-extensions" : [