Bump ionicons from 5.5.4 to 6.0.0 in /searx/static/themes/simple

Bumps [ionicons](https://github.com/ionic-team/ionicons) from 5.5.4 to 6.0.0.
- [Release notes](https://github.com/ionic-team/ionicons/releases)
- [Commits](https://github.com/ionic-team/ionicons/compare/v5.5.4...v6.0.0)

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

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

searx/static/themes/simple/package.json

@@ -13,7 +13,7 @@
     "grunt-eslint": "^24.0.0",
     "grunt-stylelint": "^0.16.0",
     "grunt-image": "^6.4.0",
-    "ionicons": "^5.5.4",
+    "ionicons": "^6.0.0",
     "less": "^4.1.1",
     "less-plugin-clean-css": "^1.5.1",
     "stylelint": "^13.13.1",