Update zowe-high-availability.md

[ArooshLele]

The link displays the Page Not Found error message. I added the (.md) syntax at the end of the URL to resolve the problem.

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[github-actions]

📌 The subject area label is missing. Add an area: label so we know what your content is about.

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💾 The release label is missing. Add a release: label so your content is published with the correct major Zowe release.

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[github-actions]

🚀 Deployed on https://67876482b7d2c8c5066d393b--zowe-docs-master.netlify.app

[ArooshLele]

Thank you, @janan07