Bump grunt from 1.5.3 to 1.6.1 in /searx/static/themes/simple

Bumps [grunt](https://github.com/gruntjs/grunt) from 1.5.3 to 1.6.1.
- [Release notes](https://github.com/gruntjs/grunt/releases)
- [Changelog](https://github.com/gruntjs/grunt/blob/main/CHANGELOG)
- [Commits](https://github.com/gruntjs/grunt/compare/v1.5.3...v1.6.1

)

---
updated-dependencies:
- dependency-name: grunt
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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