chore: fix lint errors (#6620)

gogs.go

@@ -1,3 +1,4 @@
+//go:build go1.14
 // +build go1.14
 
 // Copyright 2014 The Gogs Authors. All rights reserved.

internal/auth/pam/pam_stub.go

@@ -1,3 +1,4 @@
+//go:build !pam
 // +build !pam
 
 // Copyright 2014 The Gogs Authors. All rights reserved.

internal/cmd/cert_stub.go

@@ -1,9 +1,11 @@
+//go:build !cert
 // +build !cert
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Copyright 2014 The Gogs Authors. All rights reserved.
 // Use of this source code is governed by a MIT-style
 // license that can be found in the LICENSE file.
+
 package cmd
 
 import (