Prepare for `@nextcloud/vue` v8

[susnux]

The next @nextcloud/vue version, version 8, has some breaking changes as some deprecated components and properties were removed. For notes at least this places need to be adjusted:

• Deprecated NcAppNavigationCounter was removed and should replaced with NcCounterBubble

  • notes/src/components/CategoriesList.vue

    Line 9 in 4137f0b

    <NcAppNavigationCounter slot="counter">

• Deprecated NcMultiselect was removed and should be replaced with NcSelect

  • notes/src/components/Sidebar.vue

    Line 25 in 50a8500

    <NcMultiselect id="category"

Both replacements are already available in current 7.x release, migration is already possible.
For more information see this tracker issue nextcloud-libraries/nextcloud-vue#4223

[joshtrichards]

Closed by #1004 and #1318