Add dummy migration for migration rollback testing

[zubair-arbi]

Jira Ticket: EDLY-1708
Related Ticket: EDLY-911

This branch was create to create a dummy migration which can be used by the devops to test release rollback including the migrations.

Testing Instructions:

1. Create a new dummy release tag for testing this change on stage multisites edly-test-1.1.0
2. Devops will deploy this release tag
3. Verify that changes are on stage (the dummy_field in EdlyUserProfile model)
4. Devops will rollback this release by reverting to previous stable release tag edly-2.3.0 (https://github.com/edly-io/edx-platform/releases/tag/edly-2.3.0)
5. Verify that ansible playbook for rollback is successfully commpleted without any error
6. Verify that the changes are stage (the dummy_field in EdlyUserProfile model) were reverted

Note: Don't merge this PR. Its created for testing purpose only.

[zubair-arbi]

@ziafazal @NIXKnight @jamshedali20 I have created this PR with a test migration for release rollback testing.

I have also create the test release https://github.com/edly-io/edx-platform/releases/tag/edly-test-1.0.0 against it.