[BUG] Wrong endReached index passed from GroupedVirtuoso

[execto]

There is wrong endReached index passed from GroupedVirtuoso.

Reproduction:
https://codesandbox.io/s/epic-brattain-np7dsp?file=/App.js

To Reproduce
Go to the end of list, and see console output. There is last index of element is 522 (logged by endReached callback), but real item index is 499. GroupedVirtuoso counts also group headers as items.

Expected behavior
Pass to endReached last real item index.

Environment
Web: Google Chrome Version 116.0.5845.110 (Official Build) (64-bit)
Forked from here https://virtuoso.dev/scroll-to-group/ and only added endReached callback