Clarify PSNativeCommandPreserveBytePipe is mainstream

[surfingoldelephant]

PR Summary

In this PR:

• Clarifies that the PSNativeCommandPreserveBytePipe feature is mainstream in PS 7.4. The previous verbiage in about_Pipelines wasn't particularly clear.
• Fixes a minor typo in about_Pipelines.
• Fixes the wrong link reference used for PSNativeCommandPreserveBytePipe in What's New in PowerShell 7.4.
  • The linked doc has also been changed to about_Pipelines, as this explicitly mentions the (now mainstream) feature by name.

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributor's guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

PoliCheck Scan Report

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[learn-build-service-prod]

Learn Build status updates of commit 76baae2:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/7.4/Microsoft.PowerShell.Core/About/about_Pipelines.md	✅Succeeded	View (powershell-7.4)
reference/7.5/Microsoft.PowerShell.Core/About/about_Pipelines.md	✅Succeeded	View (powershell-7.5)
reference/7.6/Microsoft.PowerShell.Core/About/about_Pipelines.md	✅Succeeded	View (powershell-7.6)
reference/docs-conceptual/whats-new/What-s-New-in-PowerShell-74.md	✅Succeeded	View (>=powershell-5.1)

For more details, please refer to the build report.