Change to use pwsh to have consistent JSON conversion for DateTime

[daxian-dbw]

PR Summary

ConvertTo-Json has different behavior when it comes to DateTime type in Windows PowerShell and PowerShell Core

## pwsh
PS:6> $dateTime = [datetime]::UtcNow
PS:7> $dateTime = [datetime]::new($dateTime.Ticks - ($dateTime.Ticks % [timespan]::TicksPerSecond), $dateTime.Kind)
PS:8> @{ datetime = $dateTime } | ConvertTo-Json
{
  "datetime": "2019-11-19T22:32:50Z"
}

## powershell.exe
PS:11> $dateTime = [datetime]::UtcNow
PS:12> $dateTime = [datetime]::new($dateTime.Ticks - ($dateTime.Ticks % [timespan]::TicksPerSecond), $dateTime.Kind)
PS:13> @{ datetime = $dateTime } | ConvertTo-Json
{
    "datetime":  "\/Date(1574202819000)\/"
}

tools/releaseBuild/setReleaseTag.ps1 uses the DateTime as a property for the JSON file. Change the ymal file to use pwsh instead of powershell to get consistent behavior.

PR Context

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• 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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  • Experimental feature(s) needed
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  • Documentation needed
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  • N/A or can only be tested interactively
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  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
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    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).

[daxian-dbw]

This is a simple change that make the build use pwsh instead of powershell.exe. I will just merge it.

[ghost]

🎉v7.1.0-preview.1 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes