Update dependency grunt-gh-pages to v2.1.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
grunt-gh-pages	devDependencies	minor	2.0.0 -> 2.1.0

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Release Notes

tschaub/grunt-gh-pages

### [`v2.1.0`](https://togithub.com/tschaub/grunt-gh-pages/blob/master/changelog.md#​210) [Compare Source](https://togithub.com/tschaub/grunt-gh-pages/compare/v2.0.0...v2.1.0) Upgrade to `q-io@2.0.6` based on npm audit.

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