fix versionadded directives

* The `url` option was added in version 2.3.10 of the SwiftmailerBundle
  (see symfony/swiftmailer-bundle#118).
* The `timeout` and `source_ip` options are part of SwiftmailerBundle
  since symfony/swiftmailer-bundle#14 which was part of the 2.1.0
  release.
* The `local_domain` option was first included in the 2.4.0 release (see
  symfony/swiftmailer-bundle#141).

Author: xabbuh

reference/configuration/swiftmailer.rst

@@ -46,9 +46,6 @@ url
 
 **type**: ``string``
 
-.. versionadded:: 2.4.2
-    The ``url`` option was added in SwiftMailerBundle 2.4.2.
-
 The entire SwiftMailer configuration using a DSN-like URL format.
 
 Example: ``smtp://user:pass@host:port/?timeout=60&encryption=ssl&auth_mode=login&...``
@@ -100,28 +97,22 @@ timeout
 
 **type**: ``integer``
 
-.. versionadded:: 2.4.2
-    The ``timeout`` option was added in SwiftMailerBundle 2.4.2.
-
 The timeout in seconds when using ``smtp`` as the transport.
 
 source_ip
 ~~~~~~~~~
 
 **type**: ``string``
 
-.. versionadded:: 2.4.2
-    The ``source_ip`` option was added in SwiftMailerBundle 2.4.2.
-
 The source IP address when using ``smtp`` as the transport.
 
 local_domain
 ~~~~~~~~~~~~
 
 **type**: ``string``
 
-.. versionadded:: 2.4.2
-    The ``local_domain`` option was added in SwiftMailerBundle 2.4.2.
+.. versionadded:: 2.4.0
+    The ``local_domain`` option was introduced in SwiftMailerBundle 2.4.0.
 
 The domain name to use in ``HELO`` command.