Link fixes from issues in doc site repo

[janan07]

Describe your pull request here: Users pointed out some broken links after user section reorg. This PR addresses those issues

List the file(s) included in this PR: using-api-mediation-layer.md, api-medation-sso.md, zowe-architecture.md, zowe-security-authentication.md

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[github-actions]

📁 The PR description is missing the file name(s) for the updated content. List all the files included in this PR so this information displays in our Zowe Docs GitHub Slack channel.

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[github-actions]

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