Frontend: Replace "Canceled" with "Available"

[elizabethfoster02]

Purpose
We got this feedback from the client -- but they'd prefer if we changed the name of "canceled" shifts to "available" shifts. Please change every frontend instance of "canceled" to be "available"

TODO

• Claim this ticket by adding your name and moving to "In Progress"
• Get updated with the codebase
  • git checkout dev
  • git pull
  • THEN create a new branch as per usual
  • npm install (this updates your dependencies)
  • npm run dev
• Implement description above
• Create a PR for this ticket
• Move this ticket into "Ready for Review"

Testing

• Desktop
• Mobile