Properly set script_location for alembic

[nstoik]

https://github.com/nstoik/farm_device/blob/e3e520e99d3a8db34eb6f5920df2dcd780c3d817/device/migrations/alembic.ini#L5C26-L5C26

When trying to downgrade an alembic version inside a docker container (docker exec -it, for troubleshooting), this command:

(device) fd@e321a9d9480a:/workspaces/device$ alembic -c /workspaces/device/migrations/alembic.ini history

was giving the following error:

  FAILED: Path doesn't exist: '/workspaces/device/alembic'.  Please use the 'init' command to create a new scripts folder.

This indicates that the script_location setting is incorrect. It should possibly be migrations instead of alembic.

Also should add a command to downgrade via the cli. Either -1 or a specific revision.