minor #12757 Fix a typo in mailer docs (Mutliple -> Multiple) (pableu)

This PR was merged into the 4.4 branch.

Discussion
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Fix a typo in mailer docs (Mutliple -> Multiple)

Commits
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b281628 fix a typo in mailer docs (Mutliple -> Multiple)

Author: javiereguiluz

mailer.rst

@@ -703,7 +703,7 @@ you have a transport called ``async``, you can route the message there:
 Thanks to this, instead of being delivered immediately, messages will be sent to
 the transport to be handled later (see :ref:`messenger-worker`).
 
-Mutliple Email Transports
+Multiple Email Transports
 -------------------------
 
 .. versionadded:: 4.4