LibJS/Tests: Fix this value error test description in a PlainDate test

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/38645347a79
Pull-request: https://github.com/SerenityOS/serenity/pull/8940
Reviewed-by: https://github.com/IdanHo ✅

Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.calendar.js

@@ -7,7 +7,7 @@ describe("correct behavior", () => {
 });
 
 test("errors", () => {
-    test("this value must be a Temporal.Duration object", () => {
+    test("this value must be a Temporal.PlainDate object", () => {
         expect(() => {
             Reflect.get(Temporal.PlainDate.prototype, "calendar", "foo");
         }).toThrowWithMessage(TypeError, "Not a Temporal.PlainDate");