LibJS/Tests: Use eval() for toEvalTo(), not Function()

Since we have had eval() for a while now, we can finally use it here -
this allows us to get rid of the confusing return statements in tested
source code.

Userland/Libraries/LibJS/Tests/operators/ternary-basic.js

@@ -16,5 +16,5 @@ test("object values", () => {
 });
 
 test("issue #4409, '?.' followed by decimal digit", () => {
-    expect("return false?.1:.2").toEvalTo(0.2);
+    expect("false?.1:.2").toEvalTo(0.2);
 });