[strong] fix strong object exception messages

test/message/strong-object-freeze-prop.js

Index: test/message/strong-object-freeze-prop.js
diff --git a/test/mjsunit/strong/equality.js b/test/message/strong-object-freeze-prop.js
similarity index 57%
copy from test/mjsunit/strong/equality.js
copy to test/message/strong-object-freeze-prop.js
index 5e2464c372771df089ee5117ca66a571b35172b2..17250158d56e9c8430906fc73eb27b3ce7cac6fb 100644
--- a/test/mjsunit/strong/equality.js
+++ b/test/message/strong-object-freeze-prop.js
@@ -4,7 +4,8 @@
 
 // Flags: --strong-mode
 
-(function NoSloppyEquality() {
-  assertThrows("'use strong'; 0 == 0", SyntaxError);
-  assertThrows("'use strong'; 0 != 0", SyntaxError);
-})();
+"use strong";
+
+let o = {};
+Object.defineProperty(o, "foo", { writable: true });
+Object.defineProperty(o, "foo", { writable: false });