test-js: Use prettier and format all files

Author: https://github.com/mattco98
Commit: 6d58c48c2f
Pull-request: https://github.com/SerenityOS/serenity/pull/2689
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/builtins/String/String.js

@@ -1,9 +1,9 @@
 test("constructor properties", () => {
-    expect(String).toHaveLength(1);
-    expect(String.name).toBe("String");
+  expect(String).toHaveLength(1);
+  expect(String.name).toBe("String");
 });
 
 test("typeof", () => {
-    expect(typeof String()).toBe("string");
-    expect(typeof new String()).toBe("object");
+  expect(typeof String()).toBe("string");
+  expect(typeof new String()).toBe("object");
 });