[3.9] [doc] Fix smtplib and xml.dom.minidom mark-up (GH-22769) (GH-23380)

diff --git a/Doc/library/smtplib.rst b/Doc/library/smtplib.rst
index a88e358..c1a20fe 100644
--- a/Doc/library/smtplib.rst
+++ b/Doc/library/smtplib.rst
@@ -115,7 +115,7 @@
       If the *timeout* parameter is set to be zero, it will raise a
       :class:`ValueError` to prevent the creation of a non-blocking socket
 
-.. class:: LMTP(host='', port=LMTP_PORT, local_hostname=None,
+.. class:: LMTP(host='', port=LMTP_PORT, local_hostname=None, \
                 source_address=None[, timeout])
 
    The LMTP protocol, which is very similar to ESMTP, is heavily based on the