Bump gulp-imagemin from 9.0.0 to 9.1.0 (#3529)

Bumps [gulp-imagemin](https://github.com/sindresorhus/gulp-imagemin) from 9.0.0 to 9.1.0.
- [Release notes](https://github.com/sindresorhus/gulp-imagemin/releases)
- [Commits](sindresorhus/gulp-imagemin@v9.0.0...v9.1.0)

---
updated-dependencies:
- dependency-name: gulp-imagemin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>