Remove xid field from ReqEnd description

The xid field is not present in ReqEnd any more, as it is not needed
now that the vxid is used as the record ID. Remove it from the
description.

include/tbl/vsl_tags.h

@@ -55,7 +55,6 @@ SLTM(CLI, "CLI communication",
 
 SLTM(ReqEnd, "Client request end",
 	"Marks the end of client request.\n\n"
-	"xid\n    Transaction id.\n\n"
 	"Trxd\n     Timestamp when the request started.\n\n"
 	"Tidle\n    Timestamp when the request ended.\n\n"
 	"dTrx\n    Time to receive request\n\n"