Update release_notes.md
Update release_notes.md

Fixing the tags in the Unsubscribe transactional release note to look like the UI
katieporter/docs,Whatthefoxsays/docs,Whatthefoxsays/docs,katieporter/docs,katieporter/docs,Whatthefoxsays/docs,ksigler7/docs,sendgrid/docs,katieporter/docs,ksigler7/docs,katieporter/docs,sendgrid/docs,sendgrid/docs,ksigler7/docs