Remove support for Azure Linux 2.0

[damonbarry]

Azure Linux (aka Mariner) 2.0 went out of support in July 2025. This change removes it from our builds.

To test, I ran the CI build and end-to-end test pipelines and confirmed that they (1) didn't build/test Mariner 2.0, and (2) they succeeded.

Azure IoT Edge PR checklist:

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• I have read the contribution guidelines.
• Title of the pull request is clear and informative.
• Description of the pull request includes a concise summary of the enhancement or bug fix.

Testing Guidelines

• Pull request includes test coverage for the included changes.
• Description of the pull request includes
  • concise summary of tests added/modified
  • local testing done.