Update mailer.rst

Co-Authored-By: Oskar Stark <oskarstark@googlemail.com>

Author: gisostallenberg

mailer.rst

@@ -162,7 +162,7 @@ A ``NamedAddress`` can be created from a single string::
 
     $email = (new Email())
     // ...
-    ->from(NamedAddress::fromString('Fabien <fabien@example.com>'))
+        ->from(NamedAddress::fromString('Fabien <fabien@example.com>'))
     // ...
     ;