Add pr number to change note. [skip ci]

CHANGES.rst

@@ -61,9 +61,9 @@
 
 - :class:`gevent.local.local` is compiled with Cython on CPython. It
   was already 5 to 6 times faster due to the work on :issue:`1020`,
-  and compiling it with Cython makes it another 5 times faster, for a
+  and compiling it with Cython makes it another 5 to 6 times faster, for a
   total speed up of about 35 times. It is now in the same ball park as
-  the native :class:`threading.local` class.
+  the native :class:`threading.local` class. See :pr:`1024`.
 
 1.2.2 (2017-06-05)
 ==================