remove new rule as it doesn't work with less

Author: Marieke-C

index.js

@@ -40,7 +40,6 @@ module.exports = {
 		"stylistic/declaration-colon-space-before": "never",
 		"declaration-empty-line-before": "never",
 		"declaration-no-important": true,
-		"declaration-property-value-no-unknown": true,
 		"font-family-name-quotes": "always-where-recommended",
 		"font-family-no-duplicate-names": true,
 		"function-calc-no-unspaced-operator": true,