Updated Credential parameter description with SecureString information (part 2)

[davidsmatlak]

PR Summary

• Related to AB#1626333
• Related to Add Credential (SecureString) warnings #4985
• Updated Credential parameter description with SecureString information

Documents:
Invoke-Command
Save-Help
Start-Job
Update-Help

PR Context

Select the type(s) of documents being changed.

Cmdlet reference & about_ topics

• Version 7 content
• Version 6 content
• Version 5.1 content

Conceptual articles

• Fundamental conceptual articles
• Script sample articles
• DSC articles
• Gallery articles
• JEA articles
• WMF articles
• SDK articles

PR Checklist

• I have read the contributors guide and followed the style and process guidelines
• PR has a meaningful title
• PR is targeted at the staging branch
• All relevant versions updated
• Includes content related to issues and PRs - see Closing issues using keywords.
• This PR is ready to merge and is not Work in Progress
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the
    title and remove the prefix when the PR is ready.

[opbld34]

Docs Build status updates of commit 59e9973:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/5.1/Microsoft.PowerShell.Core/Invoke-Command.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/Save-Help.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/Start-Job.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/Update-Help.md	✅Succeeded	View (powershell-5.1)
reference/6/Microsoft.PowerShell.Core/Invoke-Command.md	✅Succeeded	View (powershell-6)
reference/6/Microsoft.PowerShell.Core/Save-Help.md	✅Succeeded	View (powershell-6)
reference/6/Microsoft.PowerShell.Core/Start-Job.md	✅Succeeded	View (powershell-6)
reference/6/Microsoft.PowerShell.Core/Update-Help.md	✅Succeeded	View (powershell-6)
reference/7/Microsoft.PowerShell.Core/Invoke-Command.md	✅Succeeded	View (powershell-7)
reference/7/Microsoft.PowerShell.Core/Save-Help.md	✅Succeeded	View (powershell-7)
reference/7/Microsoft.PowerShell.Core/Start-Job.md	✅Succeeded	View (powershell-7)
reference/7/Microsoft.PowerShell.Core/Update-Help.md	✅Succeeded	View (powershell-7)

For more details, please refer to the build report.

Note: If you changed an existing file name or deleted a file, broken links in other files to the deleted or renamed file are listed only in the full build report.