graph: fix staticcheck suggestion

From staticcheck: QF1002 - Convert untagged switch to tagged switch.

Author: yyforyongyu

graph/builder.go

@@ -1408,11 +1408,10 @@ func (b *Builder) processUpdate(msg interface{},
 		// check if we already have the most up-to-date information for
 		// that edge. If this message has a timestamp not strictly
 		// newer than what we already know of we can exit early.
-		switch {
+		switch msg.ChannelFlags & lnwire.ChanUpdateDirection {
 		// A flag set of 0 indicates this is an announcement for the
 		// "first" node in the channel.
-		case msg.ChannelFlags&lnwire.ChanUpdateDirection == 0:
-
+		case 0:
 			// Ignore outdated message.
 			if !edge1Timestamp.Before(msg.LastUpdate) {
 				return NewErrf(ErrOutdated, "Ignoring "+
@@ -1423,8 +1422,7 @@ func (b *Builder) processUpdate(msg interface{},
 
 		// Similarly, a flag set of 1 indicates this is an announcement
 		// for the "second" node in the channel.
-		case msg.ChannelFlags&lnwire.ChanUpdateDirection == 1:
-
+		case 1:
 			// Ignore outdated message.
 			if !edge2Timestamp.Before(msg.LastUpdate) {
 				return NewErrf(ErrOutdated, "Ignoring "+