Fixes #11118 - Fix typos in 5.1 topics

[sdwheeler]

PR Summary

Fix typos in 5.1 topics

• Fixes AB#255404 - Fixes Mention that clean is added in powershell 7.3 #11118
• Fixes AB#255403 - Fixes pwsh.exe not recognized #11116

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 contributors guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

Learn Build status updates of commit d2d7370:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/5.1/Microsoft.PowerShell.Core/About/about_Execution_Policies.md	✅Succeeded	View (powershell-5.1)
reference/5.1/Microsoft.PowerShell.Core/About/about_Functions.md	✅Succeeded	View (powershell-5.1)

For more details, please refer to the build report.

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