net/http: use default HTTP/2 frame scheduler

Use the default frame scheduler (currently round-robin)
rather than overriding the default with the priority scheduler.

The priority scheduler is slow, known buggy, and implements
a deprecated stream prioritization mechanism. The default
changed in x/net about a year ago, but we missed that net/http
is overriding that default.

Fixes #67706

Change-Id: I6d76dd0cc8c55eb5dec5cd7d25a5084877e8e8d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/590796
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
Auto-Submit: Damien Neil <[email protected]>

Author: neild

src/net/http/server.go

@@ -3598,9 +3598,7 @@ func (srv *Server) onceSetNextProtoDefaults() {
 	// Enable HTTP/2 by default if the user hasn't otherwise
 	// configured their TLSNextProto map.
 	if srv.TLSNextProto == nil {
-		conf := &http2Server{
-			NewWriteScheduler: func() http2WriteScheduler { return http2NewPriorityWriteScheduler(nil) },
-		}
+		conf := &http2Server{}
 		srv.nextProtoErr = http2ConfigureServer(srv, conf)
 	}
 }