Remove unneeded derivation from pscmdlet

[PaulHigin]

PR Summary

InstallHelper class does not need to derive from PSCmdlet Issue #767

PR Context

PR Checklist

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• [x] Summarized changes
• [x] Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
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• Breaking changes
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  • [ ] Documentation needed
    • [ ] Issue filed:
• User-facing changes
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• Testing - New and feature
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• Tooling
  • [x] I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
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