[3.9] bpo-37207: Update whatsnews for 3.9 (GH-21337)

corona10 · web-flow · commit 97558d6b08a6 · 2020-07-06T22:32:06.000+09:00
(cherry picked from commit b4a9263) Co-authored-by: Dong-hee Na <donghee.na92@gmail.com>
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
@@ -685,6 +685,10 @@ in nanoseconds.  The benchmarks were measured on an
 running the macOS 64-bit builds found at
 `python.org <https://www.python.org/downloads/mac-osx/>`_.
 
+* A number of Python builtins (:class:`range`, :class:`tuple`, :class:`set`, :class:`frozenset`, :class:`list`, :class:`dict`)
+  are now sped up by using :pep:`590` vectorcall protocol.
+  (Contributed by Dong-hee Na, Mark Shannon, Jeroen Demeyer and Petr Viktorin in :issue:`37207`.)
+
 
 Deprecated
 ==========
