LibJS: Remove assert function from Object.defineProperty() test

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/7636dee2cb6
Pull-request: https://github.com/SerenityOS/serenity/pull/1731
Reviewed-by: https://github.com/awesomekling

Libraries/LibJS/Tests/Object.defineProperty.js

@@ -1,7 +1,4 @@
-function assert(x) { if (!x) throw 1; }
-
 try {
-
     var o = {};
     Object.defineProperty(o, "foo", { value: 1, writable: false, enumerable: false });