event/adapter/logr/logr.go: remove the code that has no practical effect

Change-Id: I8ee44a15082d76022eea0e79aa3c60de7e0bd24a
Reviewed-on: https://go-review.googlesource.com/c/exp/+/607735
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

event/adapter/logr/logr.go

@@ -69,7 +69,6 @@ func (l *logSink) Error(err error, msg string, keysAndValues ...interface{}) {
 }
 
 func (l *logSink) log(ev *event.Event, msg string, keysAndValues []interface{}) {
-	ev.Labels = append(ev.Labels)
 	ev.Labels = append(ev.Labels, l.labels...)
 	for i := 0; i < len(keysAndValues); i += 2 {
 		ev.Labels = append(ev.Labels, newLabel(keysAndValues[i], keysAndValues[i+1]))