Removing_skill_model migration script update

[Sande3p]

Env

Repo to work on is: https://github.com/Sande3p/u-bahn-api/tree/feature/removing_skill_model

Requirements

A new migration file is to be created and that migration file should make all the changes in the DB, so when we run npm run migrations up on DEV / PROD it would adjust existent DB according to new changes while keeping the existent data.

Submission

Raise a PR against the base branch.