Update gitea-vet to check FSFE REUSE (#22004)

Related to:
- #21840
- https://gitea.com/gitea/gitea-vet/pulls/21

What it looks like when it's working:
https://drone.gitea.io/go-gitea/gitea/64040/1/5

All available SPDX license identifiers: [SPDX License
List](https://spdx.org/licenses/).

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/forms/package_form.go

@@ -1,6 +1,5 @@
 // Copyright 2022 The Gitea Authors. All rights reserved.
-// Use of this source code is governed by a MIT-style
-// license that can be found in the LICENSE file.
+// SPDX-License-Identifier: MIT
 
 package forms
 

services/packages/container/common.go

@@ -1,6 +1,5 @@
 // Copyright 2022 The Gitea Authors. All rights reserved.
-// Use of this source code is governed by a MIT-style
-// license that can be found in the LICENSE file.
+// SPDX-License-Identifier: MIT
 
 package container