Doc: fix default role usage (except in unittest mock docs)
diff --git a/Doc/library/poplib.rst b/Doc/library/poplib.rst
index bc7b3e7..45baad9 100644
--- a/Doc/library/poplib.rst
+++ b/Doc/library/poplib.rst
@@ -15,7 +15,7 @@
This module defines a class, :class:`POP3`, which encapsulates a connection to a
POP3 server and implements the protocol as defined in :rfc:`1939`. The
:class:`POP3` class supports both the minimal and optional command sets from
-:rfc:`1939`. The :class:`POP3` class also supports the `STLS` command introduced
+:rfc:`1939`. The :class:`POP3` class also supports the ``STLS`` command introduced
in :rfc:`2595` to enable encrypted communication on an already established connection.
Additionally, this module provides a class :class:`POP3_SSL`, which provides