Comment mentions not displayed correctly

[grnd-alt]

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Describe the bug
When typing @ to add a mention to a comment to select list is not displayed properly if the list is to long.

To Reproduce
Steps to reproduce the behavior:

1. Go to a deck card on a shared board with more than 3 people
2. Go to the comments tab
3. type @ in the new comment input field
4. top of the list hidden

Expected behavior
entire list visible/scrollable/ to the bottom where there is space

Screenshots

in this screenshot alice and admin should also be visible (also rendered in DOM but hidden)

PROBABLE ROOT CAUSE:
Overflow hidden in https://github.com/nextcloud-libraries/nextcloud-vue/blob/25f0661c3d194a55a283e9b8c085e587260bdf49/src/components/NcAppSidebar/NcAppSidebar.vue#L1290

could not yet check if vue-at has an option to display the selection on the bottom

[juliusknorr]

Please also assign suitable labels :)