Fix broken Install-PSResource test with warning condition incorrect in tests

[anamnavi]

PR Summary

Fixing a test introduced in #1891 where the test condition is incorrect and thus failing. I've updated the test to use -Match instead of -Contain

PR Context

PR Checklist

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• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
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[anamnavi]

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