Say "support for" instead of "support of"

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: serhiy-storchaka

Doc/library/email.policy.rst

@@ -257,7 +257,7 @@ added matters.  To illustrate::
       This method is also used by :func:`copy.replace`.
 
       .. versionchanged:: next
-         Added support of :func:`copy.replace`.
+         Added support for :func:`copy.replace`.
 
 
    The remaining :class:`Policy` methods are called by the email package code,