chore(workspace): set multiple versions to deny

[danyalprout]

Follow up to #408 to set multiple-versions = "deny" and update the codebase.

[Farukest]

Hi @danyalprout can you assign it to me, I'd like work on this ?

[Farukest]

Hi @danyalprout ,
Opened the PR before waiting for assignment. Got a bit eager :) hope that's okay..
Happy to make any changes if needed. #428

[danyalprout]

No worries at all, assigned to you