[tests] Cleanup tests that use assertOptimized()/assertUnoptimized().

test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js

Index: test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js
diff --git a/test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js b/test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js
index cf4161709609a6ee77773a39aea9169178914dde..6c429d93860c3fa2ebf0cd539076b49dbba784cd 100644
--- a/test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js
+++ b/test/mjsunit/compiler/regress-strict-equals-mixed-feedback.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --crankshaft
 
 function bar(x, y) {
   return x === y;