[gedit-plugins] build: do not always require vala

[Sébastien Wilmet <swilmet src gnome org>]

commit 33816269e077bc8477fb66e20d5edb643dcbd91b
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Mon Nov 11 18:44:20 2019 +0100

    build: do not always require vala
    
    A partial revert of:
    commit 423f2146907e759fb2647f1ae2e3257ef5bbe866
    
    but now I add a comment, because I thought there was an omission.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index f1e277f..40dd637 100644
--- a/meson.build
+++ b/meson.build
@@ -1,5 +1,5 @@
 project(
-  'gedit-plugins', ['c', 'vala'],
+  'gedit-plugins', 'c', # vala is added below if needed, with add_languages().
   version: '3.34.0',
   meson_version: '>= 0.49'
 )