Fix PSCustomObject Count/Length properties and ForEach/Where methods description.

[sethvs]

The Count/Length properties and ForEach/Where methods was actually added to a singleton PSCustomObject.

But examples show applying these methods/properties to arrays of PSCustomObject, which existed for quite some time.

Version(s) of document impacted

• Impacts 6.next document
• Impacts 6 document
• Impacts 5.1 document
• Impacts 5.0 document
• Impacts 4.0 document
• Impacts 3.0 document

Reason(s) for not updating all version of documents

• The documented feature was introduced in version (list version here) of PowerShell
• This issue only shows up in version (list version(s) here) of the document
• This PR partially fixes the issue, and issue # tracks the remaining work

[zjalexander]

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/whats-new/What-s-New-in-PowerShell-Core-61.md	✅Succeeded	View (powershell-3.0) View (powershell-4.0) View (powershell-5.0) View (powershell-5.1) View (powershell-6)

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.

[zjalexander]

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/whats-new/What-s-New-in-PowerShell-Core-61.md	✅Succeeded	View (powershell-3.0) View (powershell-4.0) View (powershell-5.0) View (powershell-5.1) View (powershell-6)

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.