[gtk-doc] fixxref: update for the index.sgml -> devhelp2 change

[Stefan Sauer <stefkost src gnome org>]

commit 10fdc9735ee0a5fb7bb597aa5d72e43af69e10cf
Author: Stefan Sauer <ensonic users sf net>
Date:   Wed Nov 8 20:00:43 2017 +0100

    fixxref: update for the index.sgml -> devhelp2 change
    
    We've forgot to update the help string.

 gtkdoc-fixxref.in |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtkdoc-fixxref.in b/gtkdoc-fixxref.in
index 0ea02d4..44f6bd1 100755
--- a/gtkdoc-fixxref.in
+++ b/gtkdoc-fixxref.in
@@ -40,7 +40,7 @@ if __name__ == '__main__':
                         help='The directory where gtk-doc generated documentation is'
                        'installed.')
     parser.add_argument('--extra-dir', default=[], action='append',
-                        help='Directories to recursively scan for indices (index.sgml)'
+                        help='Directories to recursively scan for indices (*.devhelp2)'
                         'in addition to HTML_DIR')
     parser.add_argument('--src-lang', default='c',
                         help='Programing language used for syntax highlighting. The'