Clarify that GzipFile.read1() is now implemented

diff --cc Doc/library/gzip.rst
index a2fa3fa07a5588333047ca9f6f3153ec3b9e7c56,659a027648c439615915867f74695de1cddd0884..59ea9d3432c05b964521c39e93a308357cb00a03
--- 1/Doc/library/gzip.rst
--- 2/Doc/library/gzip.rst
+++ b/Doc/library/gzip.rst
@@@ -94,6 -94,6 +94,9 @@@ The module defines the following items
     .. versionchanged:: 3.2
        Support for unseekable files was added.
  
++   .. versionchanged:: 3.3
++      The :meth:`io.BufferedIOBase.read1` method is now implemented.
++
  
  .. function:: open(filename, mode='rb', compresslevel=9)