Remove a couple of unused VSL tag definitions

Remove a couple of unused VSL tag definitions. This is safe to do now
that we are making a major release.

include/tbl/vsl_tags.h

@@ -128,8 +128,6 @@ SLTM(BackendOpen, 0, "Backend connection opened",
 	"\n"
 )
 
-SLTM(BackendXID, SLT_F_UNUSED, "The unique ID of the backend transaction", "")
-
 SLTM(BackendReuse, 0, "Backend connection put up for reuse",
 	"Logged when a backend connection is put up for reuse by a later"
 	" connection.\n\n"
@@ -393,8 +391,6 @@ SLTM(Backend_health, 0, "Backend health check",
 	"\n"
 )
 
-SLTM(VCL_Debug, SLT_F_UNUSED, "", "")
-
 SLTM(VCL_Log, 0, "Log statement from VCL",
 	"User generated log messages insert from VCL through std.log()"
 )