[atkmm] doc/reference/Doxyfile.in: Use doxygen-extra.css

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 0c854721b878f25dafc3f24b4e8ee14de2f3cdc5
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Sep 11 12:56:49 2018 +0200

    doc/reference/Doxyfile.in: Use doxygen-extra.css

 doc/reference/Doxyfile.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/doc/reference/Doxyfile.in b/doc/reference/Doxyfile.in
index d68550c..7f2717a 100644
--- a/doc/reference/Doxyfile.in
+++ b/doc/reference/Doxyfile.in
@@ -162,8 +162,8 @@ HTML_OUTPUT            = html
 HTML_FILE_EXTENSION    = .html
 HTML_HEADER            =
 HTML_FOOTER            =
-HTML_STYLESHEET        = "$(MMDOCTOOLDIR)/doxygen.css"
-HTML_EXTRA_STYLESHEET  =
+HTML_STYLESHEET        =
+HTML_EXTRA_STYLESHEET  = "$(MMDOCTOOLDIR)/doxygen-extra.css"
 HTML_EXTRA_FILES       =
 HTML_COLORSTYLE_HUE    = 220
 HTML_COLORSTYLE_SAT    = 100