Remove unused import-sql image

[nyurik]

import-sql image is not used anywhere in OMT, deleting.

[eva-j]

This will need a change in readme (documentation) I guess.

[nyurik]

@eva-j readme does not reference import-sql image. It only mentions import-sql command.

[eva-j]

Oh, I see... Instead of
docker-compose run import-sql
will be used
docker-compose run openmaptiles-tools import-sql
but in Readme there is just make import-sql which stays the same.