Recommend GitHub App authentication in the ARC quickstart

[sushant-me]

Why

The ARC quickstart currently instructs readers to generate a legacy personal access token (classic) as the default way to authenticate ARC to GitHub. For repository and organization runners, GitHub recommends authenticating with a GitHub App instead; a personal access token (classic) is only required for runners at the enterprise level.

What changed

• The authentication step in the quickstart now points readers to the existing authentication guidance and recommends a GitHub App for repository and organization runners, while noting that a personal access token (classic) is required for enterprise-level runners.
• Added a note near the PAT-based example clarifying that readers using a GitHub App should configure \githubConfigSecret\ with the app credentials (\github_app_id, \github_app_installation_id, and \github_app_private_key) instead of \github_token.

Verification

• Anchor references in the updated links match existing section headings in the authentication guide.
• No content was removed from the PAT-based example, which remains valid (and required) for enterprise-level configurations.

Closes #37288

[github-actions]

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Table of review links

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The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
actions/tutorials/use-actions-runner-controller/get-started.md	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

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[subatoi]

Reopening—closed in error, apologies.

[subatoi]

@sushant-me Thank you very much for raising a PR; however, #44450 preceded this by some time, and addresses the same issue, so I've gone ahead and approved and merged that instead. Thank you very much for your interest in the GitHub docs