Fix REST API docs help link

[mehul0810]

Summary

• Updates the Remove REST API Links help link to the live Perform documentation URL.
• Leaves the existing UTM handling and settings metadata shape unchanged.

Validation

• Verified the old URL returns HTTP 404 and the replacement URL returns HTTP 200.
• php -l src/Includes/Helpers.php
• git diff --check

Notes

• composer check-cs -- src/Includes/Helpers.php still fails on pre-existing whole-file style violations unrelated to this one-line URL change.

Closes #25.

[github-actions]

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