Types of changes

Issue #691 has highlighted a change in default behavior for the regularization of unbalanced OT. This was not properly stated in the release note but we added here a warning block in the doc of the functions to make teh change in behavior more clear.

Motivation and context / Related issue

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.