Add unit test coverage for db/repos/migrations - Closes #1589

[nazarhussain]

What was the problem?

The introduction of txIf break the transaction context which causes failure of different unit tests.

How did I fix it?

Reverted the changes and created the respective issue on pg-promise vitaly-t/pg-promise#479

How to test it?

npx mocha test/unit/db/repos/migrations.js

Review checklist

• The PR solves Add unit test coverage for db/repos/migrations #1589
• All new code is covered with unit tests
• All new code was formatted with Prettier
• Linting passes
• Tests pass
• Commit messages follow the commit guidelines
• Documentation has been added/updated