fixup rst

Author: picnixz

Misc/NEWS.d/next/Library/2024-12-11-17-44-36.gh-issue-127794.VwmRsp.rst

@@ -1,4 +1,4 @@
-When headers are added to :meth:`email.message.Message` objects, either through
+When headers are added to :class:`email.message.Message` objects, either through
 :meth:`email.message.Message.__setitem__` or :meth:`email.message.Message.add_header`,
 the field name is now validated according to  :rfc:`RFC 5322, Section 3.6.8 <5322#section-3.6.8>`
 and a :exc:`ValueError` is raised if the field name contains any invalid characters.