Remove flush_monomorphic_ics flag.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 2975d09f63de15cb16e33a0d1c19ba030b5fc976..dcf0a983074dfabe0cf0ae7e7b0588e8e7c7a169 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1350,8 +1350,6 @@ class Heap {
     global_ic_age_ = (global_ic_age_ + 1) & SharedFunctionInfo::ICAgeBits::kMax;
   }
 
-  bool flush_monomorphic_ics() { return flush_monomorphic_ics_; }
-
   int64_t amount_of_external_allocated_memory() {
     return amount_of_external_allocated_memory_;
   }
@@ -1538,8 +1536,6 @@ class Heap {
 
   int global_ic_age_;
 
-  bool flush_monomorphic_ics_;
-
   int scan_on_scavenge_pages_;
 
   NewSpace new_space_;