Bump versionchanged to 3.12

Author: arhadthedev

Doc/library/mmap.rst

@@ -281,7 +281,7 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
       Return the length of the file, which can be larger than the size of the
       memory-mapped area.
 
-      .. versionchanged:: 3.10
+      .. versionchanged:: 3.12
          For a mapping of anonymous memory, the size is now returned on both
          Unix and Windows. Previously, the size would be returned on Windows
          and an :exc:`OSError` would be raised on Unix.