Correct a typo. Found by Lauri Hakko on docs@.
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
index 83f151b..d543973 100644
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -733,7 +733,7 @@
----
:meth:`~http.server.BaseHTTPRequestHandler.send_error` now accepts an
-optional additional *exaplain* parameter which can be used to provide an
+optional additional *explain* parameter which can be used to provide an
extended error description, overriding the hardcoded default if there is one.
This extended error description will be formatted using the
:attr:`~http.server.HTTP.error_message_format` attribute and sent as the body