Replaced @returns with @return for more standard command use and compatibility.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53549 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/filefn.h

@@ -124,7 +124,7 @@ public:
     @note The generic Unix implementation depends on the system having the
           @c statfs() or @c statvfs() function.
 
-    @returns @true on success, @false if an error occurred (for example, the
+    @return @true on success, @false if an error occurred (for example, the
              directory doesn’t exist).
 
     @header{wx/filefn.h}