[DevTools] Remove build dates from extension manifests (#37306)

## Summary

The extension build writes `new Date().toLocaleDateString()` into
Chrome/Edge `version_name` and into every browser's manifest
description. That string changes with the calendar, timezone, and
locale, so a Firefox AMO rebuild on another day cannot match the
uploaded zip.

Stop stamping dates. `version_name` stays the value from the source
manifest (still updated by `prepare-release.js` on version bumps). The
description still records the commit from #37305.

Depends on #37305. Next: #37307.

## How did you test this change?

Build-script only. After this, `manifest.json` description is `Created
from revision <commit>.` and Chrome/Edge `version_name` is the committed
version string.

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Co-authored-by: Ruslan Lesiutin <hoxy@meta.com>