Update PHPMailerTest.php reference

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

README.md

@@ -162,7 +162,7 @@ To reduce PHPMailer's deployed code footprint, examples are not included if you
 
 Complete generated API documentation is [available online](https://phpmailer.github.io/PHPMailer/).
 
-You can generate complete API-level documentation by running `phpdoc` in the top-level folder, and documentation will appear in the `docs` folder, though you'll need to have [PHPDocumentor](https://www.phpdoc.org) installed. You may find [the unit tests](https://github.com/PHPMailer/PHPMailer/blob/master/test/PHPMailerTest.php) a good reference for how to do various operations such as encryption.
+You can generate complete API-level documentation by running `phpdoc` in the top-level folder, and documentation will appear in the `docs` folder, though you'll need to have [PHPDocumentor](https://www.phpdoc.org) installed. You may find [the unit tests](https://github.com/PHPMailer/PHPMailer/blob/master/test/PHPMailer/PHPMailerTest.php) a good reference for how to do various operations such as encryption.
 
 If the documentation doesn't cover what you need, search the [many questions on Stack Overflow](https://stackoverflow.com/questions/tagged/phpmailer), and before you ask a question about "SMTP Error: Could not connect to SMTP host.", [read the troubleshooting guide](https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting).