[gnome-build-meta] Update for gtk-vnc meson options changes

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 4f2f85a579600c436b4a775662dc419298e73dd6
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Jan 8 15:45:09 2021 -0600

    Update for gtk-vnc meson options changes

 elements/core-deps/gtk-vnc.bst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/elements/core-deps/gtk-vnc.bst b/elements/core-deps/gtk-vnc.bst
index 1607f700..e09feded 100644
--- a/elements/core-deps/gtk-vnc.bst
+++ b/elements/core-deps/gtk-vnc.bst
@@ -21,7 +21,7 @@ depends:
 - freedesktop-sdk.bst:bootstrap-import.bst
 variables:
   meson-local: >-
-    -Dintrospection=true
+    -Dintrospection=enabled
     -Dpulseaudio=enabled
     -Dsasl=enabled
-    -Dwith-vala=true
+    -Dwith-vala=enabled