minor #16800 [Mailer] max_per_second option configurable via DSN (gassan)

This PR was squashed before being merged into the 6.2 branch.

Discussion
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[Mailer] `max_per_second` option configurable via DSN

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AbstractTransport::setMaxPerSecond(float) was introduces in 5.1 but wan not configurable by dsn

Commits
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7fddf4d [Mailer] `max_per_second` option configurable via DSN

Author: javiereguiluz

mailer.rst

@@ -283,6 +283,15 @@ Other Options
 
         $dsn = 'smtps://smtp.example.com?ping_threshold=200'
 
+``max_per_second``
+    The number of messages to send per second (0 to disable this limitation)::
+
+        $dsn = 'smtps://smtp.example.com?max_per_second=2'
+
+    .. versionadded:: 6.2
+
+        The ``max_per_second`` option was introduced in Symfony 6.2.
+
 Creating & Sending Messages
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