Fix errors in ShouldProcess rule document

[Masaru Iritani (masaru-iritani)]

PR Summary

• Fix wrong variable names in examples.
• Remove Write-Host from the correct example. It is duplicated with outputs of -WhatIf or -Confirm. It also violates "Avoid Using Write-Host" rule.
• Correct the severity of ShouldProcess rule as mentioned in ShouldProcess.md. Get-ScriptAnalyzerRule -Name PSShouldProcess | % Severity also returns "Warning" with ScriptAnalyzer 1.20.0

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.
• Update examples can run successfully on PowerShell 7.2.1.
• Script Analyzer 1.20.0 detects a ShouldProcess violation in the updated wrong example. For some reason, Script Analyzer 1.20.0 doesn't detect any ShouldProcess violation in the updated wrong example.
• Script Analyzer 1.20.0 detects no error in the updated correct example.

[Christoph Bergmeister (bergmeister)]

Awesome, thank you for the effort and very detailed description 🥳
Sean Wheeler (@sdwheeler) I am happy from a technical perspective, do you want to review the docs change as well before merging?

[Sean Wheeler (sdwheeler)]

One minor change to link to about_* topics.

[Masaru Iritani (masaru-iritani)]

One minor change to link to about_* topics.

Updated as suggested. Would you review it again and resolve the request? I cannot find any way to resolve this thread by myself.

[Christoph Bergmeister (bergmeister)]

Sean Wheeler (@sdwheeler) Can you re-review please? You can contact James Truher (@JamesWTruher) to get it merged as the left-over check doesn't seem to go away when pulling in master.

[Christoph Bergmeister (bergmeister)]

Thanks Sean Wheeler (@sdwheeler), can you resolve the merge conflict please and then we are good to merge 💪🏻