#12761: fix wording of zlib license section

sandrotosi · sandrotosi · commit 4047d68a0565 · 2011-08-16T20:02:15.000+02:00
diff --git a/Doc/license.rst b/Doc/license.rst
@@ -917,7 +917,7 @@ zlib
 ----
 
 The :mod:`zlib` extension is built using an included copy of the zlib
-sources unless the zlib version found on the system is too old to be
+sources if the zlib version found on the system is too old to be
 used for the build::
 
   Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler
