[libsoup] meson: actually declare the gtk_doc option

[Claudio Saavedra <csaavedra src gnome org>]

commit dfc572f366bc3df0b21f8b862b305204e32034db
Author: Claudio Saavedra <csaavedra igalia com>
Date:   Thu May 16 16:31:12 2019 +0300

    meson: actually declare the gtk_doc option
    
    Forgot to change it in meson_options.txt

 meson_options.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson_options.txt b/meson_options.txt
index 774e8777..ab565c90 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -46,7 +46,7 @@ option('vapi',
   description : 'Build Vala bindings'
 )
 
-option('doc',
+option('gtk_doc',
   type: 'boolean',
   value: false,
   description: 'Enable generating the API reference'