[BUG] Address the use of Invoke-Expression

[mitchelbaker-cisa]

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Describe the bug

The Invoke-Expression cmdlet should only be used as a last resort since it has implications such as code injection. In most scenarios, safer and more robust alternatives are available.

SetupTestbed.ps1 and install_lme.ps1 are the two files which should be updated.

Additional info:
https://learn.microsoft.com/en-us/powershell/scripting/learn/deep-dives/avoid-using-invoke-expression?view=powershell-7.4
https://learn.microsoft.com/en-us/powershell/utility-modules/psscriptanalyzer/rules/avoidusinginvokeexpression?view=ps-modules

Expected behavior

Same behavior is expected, solution is to simply invoke the command directly.