session: change revoked at to tlv type 16

In this commit, we change the tlv type number for the RevokedAt field to
16 and reserve types 14 and 15 for future use.

Author: ellemouton

session/tlv.go

@@ -25,7 +25,9 @@ const (
 	typeRemotePublicKey tlv.Type = 11
 	typeMacaroonRecipe  tlv.Type = 12
 	typeCreatedAt       tlv.Type = 13
-	typeRevokedAt       tlv.Type = 14
+	typeReservedNum1    tlv.Type = 14
+	typeReservedNum2    tlv.Type = 15
+	typeRevokedAt       tlv.Type = 16
 
 	// typeMacaroon is no longer used, but we leave it defined for backwards
 	// compatibility.