archive/zip: use Time.UTC instead of Time.In(time.UTC)

The former is more succinct and readable.

Change-Id: Ic249d1261a705ad715aeb611c70c7fa91db98254
Reviewed-on: https://go-review.googlesource.com/76830
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/archive/zip/reader.go

@@ -391,7 +391,7 @@ parseExtras:
 	msdosModified := msDosTimeToTime(f.ModifiedDate, f.ModifiedTime)
 	f.Modified = msdosModified
 	if !modified.IsZero() {
-		f.Modified = modified.In(time.UTC)
+		f.Modified = modified.UTC()
 
 		// If legacy MS-DOS timestamps are set, we can use the delta between
 		// the legacy and extended versions to estimate timezone offset.

src/archive/zip/struct.go

@@ -231,7 +231,7 @@ func timeToMsDosTime(t time.Time) (fDate uint16, fTime uint16) {
 // Deprecated: Use Modified instead.
 func (h *FileHeader) ModTime() time.Time {
 	if !h.Modified.IsZero() {
-		return h.Modified.In(time.UTC) // Convert to UTC for compatibility
+		return h.Modified.UTC() // Convert to UTC for compatibility
 	}
 	return msDosTimeToTime(h.ModifiedDate, h.ModifiedTime)
 }
@@ -241,7 +241,7 @@ func (h *FileHeader) ModTime() time.Time {
 //
 // Deprecated: Use Modified instead.
 func (h *FileHeader) SetModTime(t time.Time) {
-	t = t.In(time.UTC) // Convert to UTC for compatibility
+	t = t.UTC() // Convert to UTC for compatibility
 	h.Modified = t
 	h.ModifiedDate, h.ModifiedTime = timeToMsDosTime(t)
 }