Merge pull request #2077 from lucas-clemente/speed-up-is-ack-eliciting

simplify (and speed up) IsFrameAckEliciting

internal/ackhandler/ack_eliciting.go

@@ -4,12 +4,8 @@ import "github.com/lucas-clemente/quic-go/internal/wire"
 
 // IsFrameAckEliciting returns true if the frame is ack-eliciting.
 func IsFrameAckEliciting(f wire.Frame) bool {
-	switch f.(type) {
-	case *wire.AckFrame:
-		return false
-	default:
-		return true
-	}
+	_, ok := f.(*wire.AckFrame)
+	return !ok
 }
 
 // HasAckElicitingFrames returns true if at least one frame is ack-eliciting.