Update content libraries roles and permissions documentation

[MaferMazu]

[gviedma-aulasneo]

Please, check these if you have the time @MaferMazu @mariajgrimaldi

https://openedx.atlassian.net/wiki/spaces/OEPM/pages/5353144950/Manage+library+user+access

https://openedx.atlassian.net/wiki/spaces/OEPM/pages/5374574595/DONE+AuthZ+How+tos+updates

Both are waiting for review and were already edited based on Sarina’s feedback, but it would be great if other team members could check them and see if anything else is missing.