Bump web-ext from 8.9.0 to 9.1.0

Bumps [web-ext](https://github.com/mozilla/web-ext) from 8.9.0 to 9.1.0.
- [Release notes](https://github.com/mozilla/web-ext/releases)
- [Commits](mozilla/web-ext@8.9.0...9.1.0)

---
updated-dependencies:
- dependency-name: web-ext
  dependency-version: 9.1.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]