LibJS: Indent tests with 4 spaces instead of 2

Author: https://github.com/mattco98
Commit: 1ef573eb30
Pull-request: https://github.com/SerenityOS/serenity/pull/2689
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/exception-ReferenceError.js

@@ -1,3 +1,3 @@
 test("unknown variable produces ReferenceError", () => {
-  expect(new Function("i < 3")).toThrow(ReferenceError);
+    expect(new Function("i < 3")).toThrow(ReferenceError);
 });