feat: adds sprint number to api and removes auto migration of meetings feature
This PR adds sprint number to dashboard list api. The api will now return current sprint number along with name, key and board_id.
It also removes all code related to migrating sprint retrospective meetings to google drive and posting on forum. This feature will be moved to handbook repo as part of BB-6586.
Testing instructions
- Make sure that all code and configurations related to migrating zoom meetings have been removed
- Test
/dashboard/
api.