Bump gulp-imagemin from 7.1.0 to 9.1.0 in /{{cookiecutter.project_slug}}

Bumps [gulp-imagemin](https://github.com/sindresorhus/gulp-imagemin) from 7.1.0 to 9.1.0.
- [Release notes](https://github.com/sindresorhus/gulp-imagemin/releases)
- [Commits](https://github.com/sindresorhus/gulp-imagemin/compare/v7.1.0...v9.1.0)

---
updated-dependencies:
- dependency-name: gulp-imagemin
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

{{cookiecutter.project_slug}}/package.json

@@ -14,7 +14,7 @@
     "concurrently": "^8.0.1",
     "cssnano": "^7.0.0",
     "gulp": "^4.0.2",
-    "gulp-imagemin": "^7.1.0",
+    "gulp-imagemin": "^9.1.0",
     "gulp-plumber": "^1.2.1",
     "gulp-postcss": "^10.0.0",
     "gulp-rename": "^2.0.0",