[BUGFIX] Add missing import for a type annotation in a test (#795)

Author: oliverklee

tests/Unit/Rule/RuleTest.php

@@ -9,6 +9,7 @@
 use Sabberworm\CSS\Settings;
 use Sabberworm\CSS\Rule\Rule;
 use Sabberworm\CSS\Value\RuleValueList;
+use Sabberworm\CSS\Value\Value;
 use Sabberworm\CSS\Value\ValueList;
 
 /**