[web] Fix capitalization of roles modal
Two quick changes here. The first is to change capitalization from 'Create Role' to 'Create role'. The second is the display the modal name conditionally on whether the action is to create a role or
edit a role.
- Opening the modal to create a role shows 'Create role'
- Opening the modal to edit an exisitng role shows 'Edit role'
Reviewers: atul, ginsu
Reviewed By: ginsu
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D9221