meson: Set weston-launch as disabled by default

While the option is still available, this brings more attention to the
upcoming deprecation of weston-launch.

Signed-off-by: Kenny Levinsen <kl@kl.wtf>

meson_options.txt

@@ -68,8 +68,8 @@ option(
 option(
 	'weston-launch',
 	type: 'boolean',
-	value: true,
+	value: false,
-	description: 'Weston launcher for systems without logind'
+	description: 'Deprecated weston launcher for systems without logind'
 )
 
 option(