Fix typo in docstring (GH-23515)

diff --git a/Lib/http/client.py b/Lib/http/client.py
index a54679c..4eca93e 100644
--- a/Lib/http/client.py
+++ b/Lib/http/client.py
@@ -861,7 +861,7 @@ def set_tunnel(self, host, port=None, headers=None):
         the endpoint passed to `set_tunnel`. This done by sending an HTTP
         CONNECT request to the proxy server when the connection is established.
 
-        This method must be called before the HTML connection has been
+        This method must be called before the HTTP connection has been
         established.
 
         The headers argument should be a mapping of extra HTTP headers to send