feat: Add GPG key fingerprint to SSH key fingerprints doc

[marcelocra]

Updated the title and added GPG key information.

Why:

Closes: #43237

What's being changed (if available, include any code snippets, screenshots, or gifs):

Added the GPG key fingerprint to the page.

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

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Source	Review	Production	What Changed
authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints.md	fpt ghec	fpt ghec

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[Copilot]

Pull request overview

Adds GPG fingerprint information alongside the existing SSH fingerprints documentation so readers can verify GitHub-related keys from a single reference page.

Changes:

• Update the article title to include GPG fingerprints
• Add separate ## SSH and ## GPG sections
• Add a GPG fingerprint block with a note about key rotation/expiration and retrieval locations

Comments suppressed due to low confidence (1)

content/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints.md:22

• variables.product.prodname_dotcom is marked "DO NOT USE" in data/variables/product.yml (use variables.product.github instead). Replace these instances to follow the repo’s variable conventions.

These are {% data variables.product.prodname_dotcom %}'s public key fingerprints:

{% data reusables.ssh.fingerprints %}

You can add the following ssh key entries to your `~/.ssh/known_hosts` file to avoid manually verifying {% data variables.product.prodname_dotcom %} hosts:

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

content/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints.md:23

• variables.product.prodname_dotcom is explicitly marked “DO NOT USE” in data/variables/product.yml; please replace these occurrences with the appropriate variable (likely variables.product.github or, if you specifically mean the github.com site, variables.product.prodname_dotcom_the_website).

These are {% data variables.product.prodname_dotcom %}'s public key fingerprints:

{% data reusables.ssh.fingerprints %}

You can add the following ssh key entries to your `~/.ssh/known_hosts` file to avoid manually verifying {% data variables.product.prodname_dotcom %} hosts: