Fix data race in Isolate::CheckDetachedContextsAfterGC

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 7ab87ff72dbe519e639d757b17845de3ac0a6256..2cceceac2824660a00a78612b2d0b8e6824fae5d 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2592,8 +2592,8 @@ void Isolate::CheckDetachedContextsAfterGC() {
   if (new_length == 0) {
     heap()->set_detached_contexts(heap()->empty_fixed_array());
   } else if (new_length < length) {
-    heap()->RightTrimFixedArray<Heap::FROM_GC>(*detached_contexts,
-                                               length - new_length);
+    heap()->RightTrimFixedArray<Heap::FROM_MUTATOR>(*detached_contexts,
+                                                    length - new_length);
   }
 }