Remove flask-cors Dependency

[k-macmillan]

User Story - Business Need

Flask-Cors was necessary for the old UI, but is no longer necessary with the SSUI. Remove it and all associated code.

• [ ] Ticket is understood, and QA has been contacted (if the ticket has a QA label).

User Story(ies)

As a VA Notify Engineer I want to keep our system lean and free of unused dependencies So that we have less to maintain and fewer vulnerabilities

Additional Info and Resources

• Flask-Cors pypi page
• It is imported like so: flask_cors

Acceptance Criteria

• [ ] Code that used flask_cors is removed
• [ ] flask_cors is not used in our code
• [ ] Dependency is removed from Poetry

[mjones-oddball]

Hey team! Please add your planning poker estimate with Zenhub @cris-oddball @EvanParish @k-macmillan @kalbfled @ldraney @MackHalliday @mchlwellman