Delete old migrations differences

Just to complement the selected answer (from the documentation):

Adding a version:

./doctrine migrations:version YYYYMMDDHHMMSS --add

Deleting a version:

./doctrine migrations:version YYYYMMDDHHMMSS --delete

The command does not execute any migrations code, it simply adds the specified version to the database.

More info

Either delete the migration class or add the generate version table (can't remember the exact name) and set the value to the migration you want start from.