Remove libs/clock in favor of luci-go/common/clock.

go/src/infra/libs/clock/timer.go

Index: go/src/infra/libs/clock/timer.go
diff --git a/go/src/infra/libs/clock/timer.go b/go/src/infra/libs/clock/timer.go
deleted file mode 100644
index f9885c34743165b8c6ae5f88d5ff24462bc5b931..0000000000000000000000000000000000000000
--- a/go/src/infra/libs/clock/timer.go
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package clock
-
-import (
-	"time"
-)
-
-// Timer is a wrapper around the time.Timer structure.
-type Timer interface {
-	GetC() <-chan time.Time     // Returns the underlying timer's channel, or nil if not configured.
-	Reset(d time.Duration) bool // See time.Timer.
-	Stop() bool                 // See time.Timer.
-}