Add migration for removing ShortendLink

[AetherUnbound]

Description

This model was deprecated in #169 and removed in #295, but did not include a migration for removing it from the database. This PR adds that migration.

Testing Instructions

1. just up
2. docker-compose exec web python manage.py makemigrations should say No changes detected

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

Developer Certificate of Origin

Developer Certificate of Origin

Developer Certificate of Origin
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[dhruvkb]

Cool cool cool!