fix(flatpak): remove --enable-tests=no to fix HAVE_VALGRIND error

libdbusmenu's configure.ac has a bug where AM_CONDITIONAL([HAVE_VALGRIND])
is only defined when tests are enabled. Removing --enable-tests=no allows
the conditional to be properly defined.

Ref: https://bugs.launchpad.net/ubuntu/+source/libdbusmenu/+bug/1708938

flatpak/com.ccswitch.desktop.yml

@@ -49,7 +49,6 @@ modules:
       - --with-gtk=3
       - --disable-dumper
       - --disable-static
-      - --enable-tests=no
       - --disable-nls
     sources:
       - type: archive