Support slevomat/coding-standard 6.1.*

Because of this [commit](https://github.com/consistence/coding-standard/commit/1d6dc1f638fdd293333939634b7021c363e82993#diff-b5d0ee8c97c7abd7e3fa29b9a27d1780L16-R16), the last minor update of [slevomat/coding-standard](https://github.com/slevomat/coding-standard/releases) is not supported anymore.