docs(actions): add SHA pinning notes to OIDC examples

[happysnaker]

Summary

• add the SHA pinning comment reusable to OIDC workflow examples that already use full commit SHAs for third-party actions
• keep the existing third-party action notice and example structure unchanged
• make the guidance consistent across the Google Cloud Platform, AWS, Azure, HashiCorp Vault, and PyPI OIDC pages

Closes #34316

[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/how-tos/secure-your-work/security-harden-deployments/oidc-in-aws.md	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17
actions/how-tos/secure-your-work/security-harden-deployments/oidc-in-azure.md	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17
actions/how-tos/secure-your-work/security-harden-deployments/oidc-in-google-cloud-platform.md	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17
actions/how-tos/secure-your-work/security-harden-deployments/oidc-in-hashicorp-vault.md	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.21 3.20 3.19 3.18 3.17
actions/how-tos/secure-your-work/security-harden-deployments/oidc-in-pypi.md	fpt ghec	fpt ghec

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

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