Bump gulp-imagemin from 6.1.1 to 6.2.0 in /arctic/static/arctic

Bumps [gulp-imagemin](https://github.com/sindresorhus/gulp-imagemin) from 6.1.1 to 6.2.0.
- [Release notes](https://github.com/sindresorhus/gulp-imagemin/releases)
- [Commits](sindresorhus/gulp-imagemin@v6.1.1...v6.2.0)

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

arctic/static/arctic/package.json

@@ -39,7 +39,7 @@
     "gulp-cssnano": "^2.1.3",
     "gulp-extname": "^0.2.2",
     "gulp-if": "^3.0.0",
-    "gulp-imagemin": "^6.1.1",
+    "gulp-imagemin": "^6.2.0",
     "gulp-load-plugins": "^2.0.1",
     "gulp-sass": "^4.0.2",
     "gulp-sourcemaps": "^2.6.5",