Update dependency grunt to ^1.6.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
grunt (source)	^1.5.3 -> ^1.6.0

---

Release Notes

gruntjs/grunt

### [`v1.6.0`](https://togithub.com/gruntjs/grunt/releases/tag/v1.6.0) [Compare Source](https://togithub.com/gruntjs/grunt/compare/v1.5.3...v1.6.0) - Merge pull request [#​1750](https://togithub.com/gruntjs/grunt/issues/1750) from gruntjs/dep-update-jan28 [`2805dc3`](https://togithub.com/gruntjs/grunt/commit/2805dc3) - README updates [`3f1e423`](https://togithub.com/gruntjs/grunt/commit/3f1e423) - Bump to 16 [`8fd096d`](https://togithub.com/gruntjs/grunt/commit/8fd096d) - Update more deps [`42c5f95`](https://togithub.com/gruntjs/grunt/commit/42c5f95) - Bump eslint and node version [`1d88050`](https://togithub.com/gruntjs/grunt/commit/1d88050)

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR has been generated by Mend Renovate. View repository job log here.