Update grunt-exec requirement from ~1.0.1 to ~3.0.0

Updates the requirements on [grunt-exec](https://github.com/jharding/grunt-exec) to permit the latest version.
- [Release notes](https://github.com/jharding/grunt-exec/releases)
- [Commits](jharding/grunt-exec@v1.0.1...v3.0.0)

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

Author: dependabot-preview[bot]

package.json

@@ -16,7 +16,7 @@
     "grunt-contrib-sass": "~1.0.0",
     "grunt-contrib-uglify": "~4.0.1",
     "grunt-contrib-watch": "~1.1.0",
-    "grunt-exec": "~1.0.1",
+    "grunt-exec": "~3.0.0",
     "grunt-open": "0.2.3",
     "matchdep": "~2.0.0"
   }