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/automatic-semicolon-insertion.js

@@ -37,7 +37,7 @@ test("break/continue, variable declaration, do-while, and return asi", () => {
     1;
 var curly/* semicolon inserted here */}
 
-return foo();`;
+foo();`;
 
     expect(source).toEvalTo(undefined);
 });
@@ -55,7 +55,7 @@ for (let i = 0; i < 5; ++i) {
     counter++;
 }
 
-return counter;`;
+counter;`;
 
     expect(source).toEvalTo(5);
 });

Userland/Libraries/LibJS/Tests/comments-basic.js

@@ -7,7 +7,7 @@ var i = 0;
 i++;
 */
 /**/ i++;
-return i;`;
+i;`;
 
     expect(source).toEvalTo(1);
 });
@@ -22,7 +22,7 @@ i++;
 --> i++;
 /**/ --> i++;
 j --> i++;
-return i;`;
+i;`;
     expect(source).toEvalTo(2);
 });
 

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);
 });

Userland/Libraries/LibJS/Tests/test-common-tests.js

@@ -333,13 +333,11 @@ test("toEval", () => {
     expect("function foo() { return 1; }; foo();").toEval();
 });
 
-// FIXME: Will have to change when this matcher changes to use the
-// "eval" function
 test("toEvalTo", () => {
     expect("let a = 1").toEvalTo();
     expect("let a = 1").toEvalTo(undefined);
-    expect("return 10").toEvalTo(10);
-    expect("return 10").not.toEvalTo(5);
+    expect("10").toEvalTo(10);
+    expect("10").not.toEvalTo(5);
 
     expect(() => {
         expect("*^&%%").not.toEvalTo();

Userland/Libraries/LibJS/Tests/test-common.js

@@ -354,7 +354,7 @@ class ExpectationError extends Error {
             let result;
 
             try {
-                result = new Function(this.target)();
+                result = eval(this.target);
             } catch (e) {
                 throw new ExpectationError();
             }