Fix requireAllExcept runtime error (#100)

Author: Sam-61s

lib/keywords/requireAllExcept.js

@@ -12,7 +12,7 @@ const compile = async (schema, _ast, parentSchema) => {
   const propertyNames = Browser.typeOf(propertiesSchema) === "object" ? Browser.keys(propertiesSchema) : [];
 
   const required = new Set(propertyNames);
-  requireAllExcept.forEach((propertyName) => propertyNames.remove(propertyName));
+  requireAllExcept.forEach((propertyName) => required.delete(propertyName));
   return [...required];
 };