This is a follow-up of MDL-65273.

Steps to reproduce:

• Login as teacher
• Go to a course
• Add an activity
• View the activity
• Open the activity's cog menu
• Click Permissions
• Click on the "plus" icon in some arbitrary row
• A popup will open which shows you a set of buttons with roles.

Actual results:

• The buttons are displayed inline and are wrapped to the next line.

Expected result:

• The buttons are displayed one per line, like we see it already in the "Add a block" modal: