Data verification 'select cell range' dialog should not scroll with sheet

[Corbe30]

Describe the bug
'select cell range' dialog scrolls with the sheet, not allowing user to select the cells behind the dialog.

To Reproduce
Steps to reproduce the behavior:

1. click on data verification
2. select the right-side icon in the input box of Cell Range field
3. this opens the 'select cell range' dialog. try to scroll

Expected behavior
The dialog stays put while the sheet scrolls, just like in Google Sheets.