[amtk] build: switch gtk_doc option to true

[Sébastien Wilmet <swilmet src gnome org>]

commit d6c332f2ad81cea5c13a3874abf8ca0a15511a99
Author: Sébastien Wilmet <swilmet informatique-libre be>
Date:   Sun Apr 17 16:48:56 2022 +0200

    build: switch gtk_doc option to true
    
    The default values in meson_options.txt are tuned for Linux
    distributors.
    
    And I recommend Linux packagers to build the gtk-doc of Amtk, so that
    it's easier for app developers to install e.g. a -devel package, launch
    Devhelp and access the docs.

 meson_options.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson_options.txt b/meson_options.txt
index bfbe49c..6897b79 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -6,6 +6,6 @@ option(
 
 option(
   'gtk_doc',
-  type: 'boolean', value: false,
+  type: 'boolean', value: true,
   description: 'Build API reference (requires gtk-doc)'
 )