Permissions Branch: Modal menus are cutoff

[wuwinson]

Steps to reproduce the behavior

Share board modal

1. Go to share board modal
2. Add a few users to the board
3. Find a user towards the bottom of the share board modal that was recently added to the board
4. Select the role dropdown to change their role
5. See error - menu is cut toff

Card view modal

1. Open a card
2. Create a multi-select property and add 10+ values
3. Click on the multi-select field to assign a value
4. See error - menu is cut off

Expected behavior

Modal should auto scroll down so user can see the full height of the menu.

Screenshots (optional)

Edition and Platform

• Edition: Mattermost Boards (plugin)
• Version: permissions-feature-branch
• Browser and OS: Chrome on Mac

[chenilim]

@asaadmahmood please investigate. Thanks.