[All Hosts] (manifest) Remove preview lingo about unified manifest

[Rick-Kirkham]

NOTE TO REVIEWERS: I have deliberately not updated the metadata dates. This seems like a paradigmatic case where it would be misleading to do so.

Do not merge until GA of WXP support in the unified manifest.

[learn-build-service-prod]

Learn Build status updates of commit d5ef085:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/concepts/privacy-and-security.md	✅Succeeded	View
docs/design/built-in-button-integration.md	✅Succeeded	View
docs/design/content-add-ins.md	✅Succeeded	View
docs/design/contextual-tabs.md	✅Succeeded	View
docs/design/custom-tab-placement.md	✅Succeeded	View
docs/design/disable-add-in-commands.md	✅Succeeded	View
docs/develop/add-in-manifests.md	✅Succeeded	View
docs/develop/agents-toolkit-overview.md	✅Succeeded	View
docs/develop/automatically-open-a-task-pane-with-a-document.md	✅Succeeded	View
docs/develop/automatically-open-on-installation.md	✅Succeeded	View
docs/develop/configure-your-add-in-to-use-a-shared-runtime.md	✅Succeeded	View
docs/develop/convert-xml-to-json-manifest.md	✅Succeeded	View
docs/develop/create-addin-commands-unified-manifest.md	✅Succeeded	View
docs/develop/dialog-api-in-office-add-ins.md	✅Succeeded	View
docs/develop/get-the-whole-document-from-an-add-in-for-powerpoint-or-word.md	✅Succeeded	View
docs/develop/json-manifest-overview.md	✅Succeeded	View
docs/develop/requesting-permissions-for-api-use-in-content-and-task-pane-add-ins.md	✅Succeeded	View
docs/develop/show-hide-add-in.md	✅Succeeded	View
docs/develop/support-for-task-pane-and-content-add-ins.md	✅Succeeded	View
docs/develop/unified-manifest-overview.md	✅Succeeded	View
docs/includes/unified-manifest-support-note.md	✅Succeeded	n/a (file deleted or renamed)
docs/quickstarts/fluent-react-quickstart.md	✅Succeeded	View
docs/tutorials/excel-tutorial.md	✅Succeeded	View

For more details, please refer to the build report.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 issues. Other issues are also a high priority. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

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