BAAS-20636: remove method from session interface

(cherry picked from commit 0dc52fd)

mongo/session.go

@@ -136,8 +136,6 @@ type Session interface {
 	// AdvanceOperationTime advances the operation time for a session. This method returns an error
 	// if the session has ended.
 	AdvanceOperationTime(*primitive.Timestamp) error
-
-	session()
 }
 
 // XSession is an unstable interface for internal use only.
@@ -373,10 +371,6 @@ func (s *sessionImpl) Client() *Client {
 	return s.client
 }
 
-// session implements the Session interface.
-func (*sessionImpl) session() {
-}
-
 // sessionFromContext checks for a sessionImpl in the argued context and returns the session if it
 // exists
 func sessionFromContext(ctx context.Context) *session.Client {