Description of the issue

The role list shown after the click action on role drop-down from "Grant role" dialog was not aligned in model boundary. 
See the snapshot as below

Steps to reproduce:

1. Launch OCM UI staging.
2. Open a ROSA cluster.
3. Go to "Access control" tab > OCM Roles and access.
4. Click "Grant role".
5. Click "Role" drop-down and see the layout.

Actual results:
The role list was not aligned with dialog model boundary .

Expected results:

The role list should be shown within the dialog model boundary.