Bump shelljs and grunt-contrib-jshint

Removes [shelljs](https://github.com/shelljs/shelljs). It's no longer used after updating ancestor dependency [grunt-contrib-jshint](https://github.com/gruntjs/grunt-contrib-jshint). These dependencies need to be updated together.


Removes `shelljs`

Updates `grunt-contrib-jshint` from 2.1.0 to 3.2.0
- [Release notes](https://github.com/gruntjs/grunt-contrib-jshint/releases)
- [Changelog](https://github.com/gruntjs/grunt-contrib-jshint/blob/main/CHANGELOG)
- [Commits](gruntjs/grunt-contrib-jshint@v2.1.0...v3.2.0)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: grunt-contrib-jshint
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -25,7 +25,7 @@
     "readmeFilename": "README.md",
     "devDependencies": {
         "grunt": "^1.4.1",
-        "grunt-contrib-jshint": "^2.1.0",
+        "grunt-contrib-jshint": "^3.2.0",
         "grunt-contrib-uglify": "^5.0.1",
         "grunt-contrib-watch": "^1.1.0",
         "grunt-exec": "^3.0.0",