Automate: An admin can control which blocks can be added to My home

This issue is about automating the testing of MDLQA-4598 & MDLQA-7082

This test requires a Moodle site in which the comments block is enabled, but has not been added to every page of the site nor to the My home page.
1. Log in as a user and click the 'Customise this page' button on your My home page.
2. Try adding a comments block to the page.
3. Delete the comments block.
4. Log in as an admin and go to Settings > Site administration > Users > Permissions > Define roles
5. Edit the authenticated user role and remove the block/comments:myaddinstance capability, then click the save changes button at the bottom of the page.
6. Log in as a user again and click the 'Customise this page' button on your My home page.
7. Check that you are no longer able to add a comments block to the page.