Remove experimental flags that are now required

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index d5f7f75c18ccb2ea6a9e5139c3b38a2c17a31139..7941cb2c0ccd3339c3d6b04a312e85304a3fc103 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -12645,15 +12645,11 @@ MaybeHandle<Object> JSObject::SetDictionaryElement(
     } else {
       new_length = dictionary->max_number_key() + 1;
     }
-    SetFastElementsCapacitySmiMode smi_mode = FLAG_smi_only_arrays
-        ? kAllowSmiElements
-        : kDontAllowSmiElements;
     bool has_smi_only_elements = false;
     bool should_convert_to_fast_double_elements =
         object->ShouldConvertToFastDoubleElements(&has_smi_only_elements);
-    if (has_smi_only_elements) {
-      smi_mode = kForceSmiElements;
-    }
+    SetFastElementsCapacitySmiMode smi_mode =
+        has_smi_only_elements ? kForceSmiElements : kAllowSmiElements;
 
     if (should_convert_to_fast_double_elements) {
       SetFastDoubleElementsCapacityAndLength(object, new_length, new_length);