Multi select field in the admin UI can't be resized

[dgarros]

Environment

• Python version: 3.7
• Nautobot version: 1.2.0b1

Steps to Reproduce

1. Go to the permissions page in the admin ui
2. Edit an existing permissions or create a new one

Expected Behavior

The multi select field to select all the object types associated with this permissions should allow the user to resize it to display more lines at the same time.

Observed Behavior

The multi select fields in the new admin UI are fixed and can only show 4 lines.
The user experience isn't great when we have a large list to select from.

[lampwins]

I know it's a bit weird because this is a reskin of the admin UI, but the StaticSelect2Multiple widget should be used here (and in any multiselect use case) for consistency.