Removed the RelationshipTypeId from Relationship endpoints

[benbosman]

References

• https://github.com/DSpace/Rest7Contract/blob/master/relationships.md#single-relationship

Description

The relationship still contained a relationshipTypeId while it was replaced with a relationshipType HAL link a long time ago. This old and incorrect property has been removed

Instructions for Reviewers

This is an unused legacy property, it's not used

Checklist

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & integration tests). Exceptions may be made if previously agreed upon.
• My PR passes Checkstyle validation based on the Code Style Guide
• My PR includes Javadoc for all new (or modified) public methods and classes. It also includes Javadoc for large or complex private methods.
• My PR passes all tests and includes new/updated Unit or Integration Tests for any bug fixes, improvements or new features. A few reminders about what constitutes good tests:
  • Include tests for different user types, including: (1) Anonymous user, (2) Logged in user (non-admin), and (3) Administrator.
  • Include tests for known error scenarios and error codes (e.g. 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, etc)
  • For bug fixes, include a test that reproduces the bug and proves it is fixed. For clarity, it may be useful to provide the test in a separate commit from the bug fix.
• If my PR includes new, third-party dependencies (in any pom.xml), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR modifies the REST API, I've linked to the REST Contract page (or open PR) related to this change.

[paulo-graca]

I've tested it yet, but this change looks ok to me.

[tdonohue]

Closing & reopening to trigger a fresh Travis rebuild. Travis hasn't rebuilt in some time & want to verify this still works fine for main (likely it does).

[tdonohue]

👍 Changes here look fine. Assuming Travis rebuild (triggered a moment ago) works, this can be merged.