[3.7] bpo-31639: Change ThreadedHTTPServer to ThreadingHTTPServer class name (GH-7195) (GH-7219)

* [3.7] bpo-31639: Change ThreadedHTTPServer to ThreadingHTTPServer class name (GH-7195).
(cherry picked from commit 1cee216cf383eade641aed22f4ec7d4cb565ecff)

* Fix whatsnew entry about ThreadedHTTPServer. (GH-7220)
(cherry picked from commit a34e424bdbc62b4d83593af1c0d459d8aaac90f3)
diff --git a/Lib/http/server.py b/Lib/http/server.py
index a2726ab..ea0e295 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -83,7 +83,7 @@
 __version__ = "0.6"
 
 __all__ = [
-    "HTTPServer", "ThreadedHTTPServer", "BaseHTTPRequestHandler",
+    "HTTPServer", "ThreadingHTTPServer", "BaseHTTPRequestHandler",
     "SimpleHTTPRequestHandler", "CGIHTTPRequestHandler",
 ]
 
@@ -140,7 +140,7 @@
         self.server_port = port
 
 
-class ThreadedHTTPServer(socketserver.ThreadingMixIn, HTTPServer):
+class ThreadingHTTPServer(socketserver.ThreadingMixIn, HTTPServer):
     daemon_threads = True
 
 
@@ -1217,7 +1217,7 @@
 
 
 def test(HandlerClass=BaseHTTPRequestHandler,
-         ServerClass=ThreadedHTTPServer,
+         ServerClass=ThreadingHTTPServer,
          protocol="HTTP/1.0", port=8000, bind=""):
     """Test the HTTP request handler class.