Remove pystone microbenchmark

Issue #15369. Please use the new "performance" benchmark suite.

Author: vstinner

Lib/test/pystone.py

@@ -16,10 +16,10 @@ Library
 Tools/Demos
 -----------
 
-- Issue #15369: The pybench microbenchmark has been removed from Tools. Please
-  use the new Python benchmark suite https://github.com/python/performance
-  which is more reliable and includes a portable version of pybench working on
-  Python 2 and Python 3.
+- Issue #15369: The pybench and pystone microbenchmark have been removed from
+  Tools. Please use the new Python benchmark suite
+  https://github.com/python/performance which is more reliable and includes a
+  portable version of pybench working on Python 2 and Python 3.
 
 - Issue #28102: The zipfile module CLI now prints usage to stderr.
   Patch by Stephen J. Turnbull.