Remove Relationships Legacy from content types

[fmontes]

Is your feature request related to a problem? Please describe.

As a stakeholder, I don't want users to be able to create content types with "Relationships Legacy" fields.

Describe the solution you'd like

1. Remove the Relationships Legacy from the backend response
2. Double check in the UI in case we need to do some clean up.

Describe alternatives you've considered

N/A

Additional context

There is a new relationship field we want the users to use.

Acceptance criteria

• Users should not be able to see Relationships Legacy in the UI
• Developers should not be able to create Relationships Legacy from the API

[fmontes]

Hey team! Please add your planning poker estimate with Zenhub @hmoreras @jcastro-dotcms @jdotcms @rjvelazco