[TASK] Make OutputFormat final (#1128)

This class is not intended to be extended, and it's intended to
be created using the factory methods anyway.

(Also, we most probably won't need to have mocks of this class
in the tests as it's mostly a data object.)

Author: oliverklee

CHANGELOG.md

@@ -21,6 +21,7 @@ Please also have a look at our
 
 ### Changed
 
+- Make `OutputFormat` `final` (#1128)
 - Mark the `OutputFormat` constructor as `@internal` (#1131) 
 - Mark `OutputFormatter` as `@internal` (#896)
 - Make `Selector` a `Renderable` (#1017)

src/OutputFormat.php

@@ -4,10 +4,7 @@
 
 namespace Sabberworm\CSS;
 
-/**
- * Extending this class is deprecated in version 8.8.0; it will be made `final` in version 9.0.0.
- */
-class OutputFormat
+final class OutputFormat
 {
     /**
      * Value format: `"` means double-quote, `'` means single-quote