(MAINT) Update PowerShell versions for latest stable

[michaeltlombardi]

PR Summary

This change updates the version strings in the install documentation to reflect the new v7.3.7 and v7.2.14 releases.

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 41d95d1:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/install/community-support.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/install-alpine.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/install-debian.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/Installing-PowerShell-on-macOS.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/Installing-PowerShell-on-Windows.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/install-other-linux.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/install-rhel.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/install-ubuntu.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/install/microsoft-update-faq.yml	✅Succeeded	View (>=powershell-5.1)

For more details, please refer to the build report.

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