Remove images that are no longer used

[sdwheeler]

PR Summary

Remove images that are no longer used in docs.

• Fixes AB#401858

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 f686d7a:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/how-to-use-docs.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/learn/shell/using-predictors.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/media/overview/linux-desktop-660.gif	✅Succeeded	n/a (file deleted or renamed)
reference/docs-conceptual/media/overview/macos-desktop-660.gif	✅Succeeded	n/a (file deleted or renamed)
reference/docs-conceptual/media/overview/macos-desktop.gif	✅Succeeded	n/a (file deleted or renamed)
reference/docs-conceptual/media/overview/windows-desktop-660.gif	✅Succeeded	n/a (file deleted or renamed)
reference/docs-conceptual/media/overview/windows-desktop.gif	✅Succeeded	n/a (file deleted or renamed)
reference/media/index/av_colors_128.svg	✅Succeeded	n/a (file deleted or renamed)
reference/media/index/powershell_128.svg	✅Succeeded	n/a (file deleted or renamed)

For more details, please refer to the build report.

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