reduce workspace load on the parameter canary vtc

It now bails out due to a workspace overflow which it acually did
trigger all the time, but that remained unnoticed due to #3194

The test to multiply the cookie header 128 times (8x in the first
regex, 16x in the second) was not realistic even for "modern times",
so I do not think we should have workspaces sized by such an example.

bin/varnishtest/tests/v00004.vtc

@@ -153,8 +153,6 @@ varnish v1 -vcl+backend {
 	sub recv9 {
 		std.log("STK recv9 " + debug.stk());
 		set req.http.regex = regsub(req.http.cookie, "(.*)", "\1\1\1\1\1\1\1\1");
-		set req.http.regex = regsub(req.http.regex, "(.*)",
-		  "\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1");
 		# hey geoff, this is deliberate
 		set req.http.regex = regsub(req.http.regex,
 		  "(.*)(.{5})(.{6})(.{7})(.{8})", "/\5\4\3\2\1");