Move "Add New GCN Notice Producer" to org scope

According to https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file#about-default-community-health-files:

> If a repository has any files in its own .github/ISSUE_TEMPLATE
folder, including issue templates or a config.yml file, none of the
contents of the default .github/ISSUE_TEMPLATE folder will be used.

Fixes #2658.