Add a correct version changed notice

Author: rhpvorderman

Doc/library/gzip.rst

@@ -195,8 +195,10 @@ The module defines the following items:
    .. versionchanged:: 3.8
       Added the *mtime* parameter for reproducible output.
    .. versionchanged:: 3.11
-      Speed is improved by compressing all data at once instead of in a
-      streamed fashion.
+      streamed fashion. Calls with *mtime* set to ``0`` are delegated to
+      :func:`zlib.compress` for better speed.
+   .. versionchanged:: 3.14
+      The OS byte is guaranteed to be set to 255 when this function is used.
 
 .. function:: decompress(data)