Fix user.signingkey example

[kariya-mitsuru]

Why:

Since the value of user.signingkey is passed unchanged to gpg's --local-user parameter, the fingerprint needs to be suffixed with an exclamation mark (!).

If a fingerprint is specified without an exclamation mark, it is simply ignored.

What's being changed:

Simply added ! to the sample code.

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• [x] I have reviewed my changes in staging (look for "Automatically generated comment" and click Modified to view your latest changes).
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Writer impact (This section is for GitHub staff members only):

• [ ] This pull request impacts the contribution experience
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  • [ ] I have added a description and/or a video demo of the changes below (e.g. a "before and after video")

[welcome[bot]]

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[github-actions[bot]]

👋 Hey there spelunker. It looks like you've modified some files that we can't accept as contributions. The complete list of files we can't accept are: .devcontainer/** .github/actions-scripts/** .github/workflows/** .github/CODEOWNERS assets/fonts/** data/graphql/** Dockerfile* lib/graphql/** lib/redirects/** lib/rest/** lib/webhooks/** lib/search/indexes/** package*.json scripts/** translations/** content/actions/deployment/security-hardening-your-deployments/**

You'll need to revert all of the files you changed in that list using GitHub Desktop or git checkout origin/main <file name>. Once you get those files reverted, we can continue with the review process. :octocat:

[janiceilene]

@kariya-mitsuru Thanks so much for opening a PR! I'll get this triaged for review ⚡

In the meantime, could you revert the changes to the translated files? We only change the English content in this repository, then the changes are passed over to translators using an external service.

[vgrl]

Thanks for proposing this change @kariya-mitsuru! ⚡ I'm going to make a few small edits to make it clear that including the ! is needed only when specifying a subkey, and then I'll merge this. 🎉

[github-actions[bot]]

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