Bump grunt-contrib-concat in /searx/static/themes/simple

Bumps [grunt-contrib-concat](https://github.com/gruntjs/grunt-contrib-concat) from 1.0.1 to 2.0.0.
- [Release notes](https://github.com/gruntjs/grunt-contrib-concat/releases)
- [Changelog](https://github.com/gruntjs/grunt-contrib-concat/blob/main/CHANGELOG)
- [Commits](https://github.com/gruntjs/grunt-contrib-concat/compare/v1.0.1...v2.0.0)

---
updated-dependencies:
- dependency-name: grunt-contrib-concat
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

searx/static/themes/simple/package.json

@@ -3,7 +3,7 @@
     "grunt-cli": "^1.4.3",
     "grunt": "~1.4.1",
     "grunt-contrib-copy": "^1.0.0",
-    "grunt-contrib-concat": "~1.0.1",
+    "grunt-contrib-concat": "~2.0.0",
     "grunt-contrib-cssmin": "^4.0.0",
     "grunt-contrib-jshint": "~3.1.1",
     "grunt-contrib-less": "~3.0.0",