time: remove unused parameter

lookupName is only called in one location, and one of the return
values is unused, so let's remove it.

Change-Id: I35e22c7ec611e8eb349deb4f0561e212f7d9de0b
Reviewed-on: https://go-review.googlesource.com/55232Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>

src/time/format.go

@@ -1071,7 +1071,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 		t := Date(year, Month(month), day, hour, min, sec, nsec, UTC)
 		// Look for local zone with the given offset.
 		// If that zone was in effect at the given time, use it.
-		offset, _, ok := local.lookupName(zoneName, t.unixSec())
+		offset, ok := local.lookupName(zoneName, t.unixSec())
 		if ok {
 			t.addSec(-int64(offset))
 			t.setLoc(local)

src/time/zoneinfo.go

@@ -223,7 +223,7 @@ func (l *Location) firstZoneUsed() bool {
 // lookupName returns information about the time zone with
 // the given name (such as "EST") at the given pseudo-Unix time
 // (what the given time of day would be in UTC).
-func (l *Location) lookupName(name string, unix int64) (offset int, isDST bool, ok bool) {
+func (l *Location) lookupName(name string, unix int64) (offset int, ok bool) {
 	l = l.get()
 
 	// First try for a zone with the right name that was actually
@@ -235,9 +235,9 @@ func (l *Location) lookupName(name string, unix int64) (offset int, isDST bool,
 	for i := range l.zone {
 		zone := &l.zone[i]
 		if zone.name == name {
-			nam, offset, isDST, _, _ := l.lookup(unix - int64(zone.offset))
+			nam, offset, _, _, _ := l.lookup(unix - int64(zone.offset))
 			if nam == zone.name {
-				return offset, isDST, true
+				return offset, true
 			}
 		}
 	}
@@ -246,7 +246,7 @@ func (l *Location) lookupName(name string, unix int64) (offset int, isDST bool,
 	for i := range l.zone {
 		zone := &l.zone[i]
 		if zone.name == name {
-			return zone.offset, zone.isDST, true
+			return zone.offset, true
 		}
 	}