build(deps-dev): bump grunt-exec

Bumps [grunt-exec](https://github.com/jharding/grunt-exec) from 0.4.6 to 0.4.7.
- [Release notes](https://github.com/jharding/grunt-exec/releases)
- [Commits](jharding/grunt-exec@v0.4.6...v0.4.7)

---
updated-dependencies:
- dependency-name: grunt-exec
  dependency-version: 0.4.7
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

test-app/build-tools/android-metadata-generator/package.json

@@ -15,7 +15,7 @@
     "grunt": "0.4.5",
     "grunt-contrib-clean": "0.5.0",
     "grunt-contrib-copy": "0.5.0",
-    "grunt-exec": "0.4.6",
+    "grunt-exec": "0.4.7",
     "node-fs" : "0.1.7"
   }
 }