hgweb: simplify a constant-length list by converting to literal tuple

The call to `.append()` has been unnecessary since d3dbdca92458
(hgweb: don't choke when an inexistent style is requested (issue1901),
2009-11-12).

Differential Revision: https://phab.mercurial-scm.org/D8898

mercurial/hgweb/hgweb_mod.py

@@ -79,8 +79,7 b' def _stylemap(styles, path=None):'
                 and pycompat.osaltsep in style
             ):
                 continue
-            locations = [os.path.join(style, b'map'), b'map-' + style]
-            locations.append(b'map')
+            locations = (os.path.join(style, b'map'), b'map-' + style, b'map')
 
             for location in locations:
                 mapfile = os.path.join(path, location)