Fix off-by-one error in Array.concat slow mode check

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 28a97cb8e201c7881c328a84b72e95dcb1388221..7adeaf754d001852778aae82e0b0a1cec1cc42d0 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -9857,8 +9857,8 @@ class ArrayConcatVisitor {
     // but the array blowing the limit didn't contain elements beyond the
     // provided-for index range, go to dictionary mode now.
     if (fast_elements_ &&
-        index_offset_ >= static_cast<uint32_t>(
-            FixedArrayBase::cast(*storage_)->length())) {
+        index_offset_ >
+            static_cast<uint32_t>(FixedArrayBase::cast(*storage_)->length())) {
       SetDictionaryMode();
     }
   }