fix: update code for golangci-lint varcheck (#17045)

Signed-off-by: Shengwen Yu <yshengwen@vmware.com>

src/.golangci.yaml

@@ -41,7 +41,7 @@ linters:
     # - unconvert
     # - unparam
     # - unused
-    # - varcheck
+    - varcheck
  
 run:
   skip-files:

src/pkg/reg/adapter/aliacr/types.go

@@ -3,9 +3,8 @@ package aliacr
 import "time"
 
 const (
-	defaultTemporaryTokenExpiredTime = time.Hour * 1 // nolint:deadcode
-	registryEndpointTpl              = "https://registry.%s.aliyuncs.com"
-	endpointTpl                      = "cr.%s.aliyuncs.com"
+	registryEndpointTpl = "https://registry.%s.aliyuncs.com"
+	endpointTpl         = "cr.%s.aliyuncs.com"
 )
 
 type authorizationToken struct {

src/pkg/reg/adapter/tencentcr/adapter.go

@@ -24,8 +24,7 @@ import (
 )
 
 var (
-	errInvalidTcrEndpoint    error = errors.New("[tencent-tcr.newAdapter] Invalid TCR instance endpoint")
-	errPingTcrEndpointFailed error = errors.New("[tencent-tcr.newAdapter] Ping TCR instance endpoint failed") // nolint:deadcode
+	errInvalidTcrEndpoint error = errors.New("[tencent-tcr.newAdapter] Invalid TCR instance endpoint")
 )
 
 func init() {