Don't be so picky about the Via header format

The default format has been changed to include the instance name
and the test only needs to check for a sensible Via header at all.

examples/rewrite/cafe.vtc

@@ -94,7 +94,7 @@ client c1 -connect "${localhost} ${localport}" {
 	txreq -url /coffee -hdr "Host: cafe.example.com"
 	rxresp
 	expect resp.status == 200
-	expect resp.http.Via ~ {^1.1 varnish \(Varnish/\d\.\d\)$}
+	expect resp.http.Via ~ {^1.1 .*Varnish}
 
 	txreq -url /coffee -hdr "Host: cafe.example.com" \
 		-hdr "Delete-Via: TRUE"