[gtk-doc] meson: bump meson dep atleast to 0.48

[Stefan Sauer <stefkost src gnome org>]

commit 5ea36b00ebb528c96df5058898a216e7d591f2ac
Author: Stefan Sauer <ensonic users sf net>
Date:   Sun May 5 14:55:51 2019 +0200

    meson: bump meson dep atleast to 0.48
    
    The build uses features fro 0.50 and I don't know how to satisfy them for 0.48.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 46277e7..080163a 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('gtk-doc', 'c',
   version: '1.29.1',
   license: 'GPL2+',
-  meson_version: '>= 0.41.0',
+  meson_version: '>= 0.48.0',
 )
 
 gnome = import('gnome')