Fix a couple of versionadded/versionchanged related markup errors.
diff --git a/Doc/library/email.parser.rst b/Doc/library/email.parser.rst
index 96fe444..54e5521 100644
--- a/Doc/library/email.parser.rst
+++ b/Doc/library/email.parser.rst
@@ -107,7 +107,8 @@
message body, instead setting the payload to the raw body as a string. They
have the same API as the :class:`Parser` and :class:`BytesParser` classes.
-.. versionadded:: 3.3 BytesHeaderParser
+.. versionadded:: 3.3
+ The BytesHeaderParser class.
.. class:: Parser(_class=email.message.Message, *, policy=policy.default)