added redirect for antiquated docs page
added redirect for antiquated docs page

https://sendgrid.com/docs/Classroom/Track/unsubscribe_via_the_subscription_tracking.html now redirects to https://sendgrid.com/docs/Classroom/Track/Unsubscribes/unsubscribe_via_subscription_tracking.html
Zaftula/docs,hardikjain29/docs,katieporter/docs,katieporter/docs,sendgrid/docs,ksigler7/docs,Aonepathan/docs,Zaftula/docs,jacobmovingfwd/docs,ksigler7/docs,Zaftula/docs,Whatthefoxsays/docs,sendgrid/docs,hardikjain29/docs,sendgrid/docs,Aonepathan/docs,jacobmovingfwd/docs,Aonepathan/docs,katieporter/docs,Whatthefoxsays/docs,katieporter/docs,Whatthefoxsays/docs,jacobmovingfwd/docs,Zaftula/docs,katieporter/docs,jacobmovingfwd/docs,hardikjain29/docs,hardikjain29/docs,Aonepathan/docs,Aonepathan/docs,ksigler7/docs,jacobmovingfwd/docs,Zaftula/docs,hardikjain29/docs