[squizlabs/php_codesniffer] Ignore `config/reference.php`

[ebitkov]

Since Symfony 8.0 (and maybe 7.4, not sure), a config/reference.php is automatically generated.

The code sniffer is reporting too long lines, but since this is an auto-generated file, we'll probably want to just ignore that.

A fix is rather simple by adding an exclude-pattern to the phpcs.xml.dist file:

    # ...
    <file>src/</file>
    <file>tests/</file>

    <exclude-pattern>config/reference.php</exclude-pattern>

</ruleset>