[Mailer] Mailtrap sandbox combine changes.

Combine changes for 7.4 additions as one single line as opposed to individual entries.

Author: KiloSierraCharlie

mailer.rst

@@ -135,8 +135,7 @@ Service               Install with                                        Webhoo
 
 .. versionadded:: 7.4
 
-    Support for Mailtrap's sandbox environment was introduced in Symfony 7.4.
-    The Microsoft Graph integration was introduced in Symfony 7.4.
+    The Microsoft Graph integration and support for Mailtrap's sandbox environment were introduced in Symfony 7.4.
 
 .. note::