Make tracked time representation display as hours (#33315)

Estimated time represented in hours it might be convenient to
have tracked time represented in the same way to be compared and
managed.

---------

Co-authored-by: Sysoev, Vladimir <i@vsysoev.ru>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/issues/stopwatch.go

@@ -46,11 +46,6 @@ func (s Stopwatch) Seconds() int64 {
 	return int64(timeutil.TimeStampNow() - s.CreatedUnix)
 }
 
-// Duration returns a human-readable duration string based on local server time
-func (s Stopwatch) Duration() string {
-	return util.SecToTime(s.Seconds())
-}
-
 func getStopwatch(ctx context.Context, userID, issueID int64) (sw *Stopwatch, exists bool, err error) {
 	sw = new(Stopwatch)
 	exists, err = db.GetEngine(ctx).
@@ -201,7 +196,7 @@ func FinishIssueStopwatch(ctx context.Context, user *user_model.User, issue *Iss
 		Doer:    user,
 		Issue:   issue,
 		Repo:    issue.Repo,
-		Content: util.SecToTime(timediff),
+		Content: util.SecToHours(timediff),
 		Type:    CommentTypeStopTracking,
 		TimeID:  tt.ID,
 	}); err != nil {