[FRONTEND] Fix access denied screen to let users know they could be logged out

[jji05]

Is your feature request related to a problem? Please describe.

Our "Access Denied" page is rather misleading as a user could just be logged out instead of "not being an admin". We should also add another quote stating the user could be logged out.

Additional context

BEFORE MERGING

• Storybooks created where possible
• Tested with react testing library
• Tests written for critical interactions
• PR Reviewed (For non-trivial changes)
• Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• All required PR checks passing