[turbofan] Relax a too-strict dcheck.

test/mjsunit/compiler/regress-v8-5573.js

Index: test/mjsunit/compiler/regress-v8-5573.js
diff --git a/test/mjsunit/regress/regress-opt-typeof-null.js b/test/mjsunit/compiler/regress-v8-5573.js
similarity index 82%
copy from test/mjsunit/regress/regress-opt-typeof-null.js
copy to test/mjsunit/compiler/regress-v8-5573.js
index e4721a18c5e0fb95a3b7cb323f229de9f605b64a..216b791a713bbb5977aeb8248924980da2a6ae2d 100644
--- a/test/mjsunit/regress/regress-opt-typeof-null.js
+++ b/test/mjsunit/compiler/regress-v8-5573.js
@@ -4,9 +4,12 @@
 
 // Flags: --allow-natives-syntax
 
+var global = true;
+global = false;
+
 function f() {
-  return typeof null === "object";
-};
+  return !global;
+}
 
 %OptimizeFunctionOnNextCall(f);
 assertTrue(f());