Correction to SIP docs (#193)
Correction to SIP docs (#193)

"X-" prefix for custom headers no longer required

Co-authored-by: Manik Sachdeva <f638dfab33d16e1e5a7f1ad0545cac425e4f76a5@gmail.com>

opentok/Opentok-Ruby-SDK,opentok/Opentok-Ruby-SDK,opentok/Opentok-Ruby-SDK