Remove unused var in objects-debug.cc

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 305cd4dafd9e1e0b3ec98b9a620a8cf81a696382..ee39fdd069c43bd2b35e2ccf27ac6ef21a3a3aed 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -1027,7 +1027,6 @@ void Box::BoxVerify() {
 }
 
 void PromiseResolveThenableJobInfo::PromiseResolveThenableJobInfoVerify() {
-  Isolate* isolate = GetIsolate();
   CHECK(IsPromiseResolveThenableJobInfo());
   CHECK(thenable()->IsJSReceiver());
   CHECK(then()->IsJSReceiver());