docs: [batch] refine proto comment for run_as_non_root (#10404)

* docs: refine proto comment for run_as_non_root docs: add caution messages for container runnable username and password fields PiperOrigin-RevId: 608240389 Source-Link: googleapis/googleapis@6f599f0 Source-Link: https://github.com/googleapis/googleapis-gen/commit/6af0d38d953e7a5f9427d650ebcd3726fe286dce Copy-Tag: eyJwIjoiamF2YS1iYXRjaC8uT3dsQm90LnlhbWwiLCJoIjoiNmFmMGQzOGQ5NTNlN2E1Zjk0MjdkNjUwZWJjZDM3MjZmZTI4NmRjZSJ9 * 🦉 Updates from OwlBot post-processor See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md --------- Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

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