`is_email_address_unsafe()` tests should only be run on multisite.

See [32638].

git-svn-id: https://develop.svn.wordpress.org/trunk@32646 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/multisite/isEmailAddressUnsafe.php

@@ -1,5 +1,7 @@
 <?php
 
+if ( is_multisite() ) :
+
 /**
  * @group multisite
  */
@@ -119,3 +121,5 @@ class Tests_Multisite_IsEmailAddressUnsafe extends WP_UnitTestCase {
 		);
 	}
 }
+
+endif;