build(deps): update dependency netlify-cli to v6.9.15

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
netlify-cli	6.9.12 -> 6.9.15

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Release Notes

netlify/cli

### [`v6.9.15`](https://togithub.com/netlify/cli/blob/master/CHANGELOG.md#​6915-httpswwwgithubcomnetlifyclicomparev6914v6915-2021-09-23) [Compare Source](https://togithub.com/netlify/cli/compare/v6.9.14...v6.9.15) ### [`v6.9.14`](https://togithub.com/netlify/cli/blob/master/CHANGELOG.md#​6914-httpswwwgithubcomnetlifyclicomparev6913v6914-2021-09-23) [Compare Source](https://togithub.com/netlify/cli/compare/v6.9.13...v6.9.14) ### [`v6.9.13`](https://togithub.com/netlify/cli/blob/master/CHANGELOG.md#​6913-httpswwwgithubcomnetlifyclicomparev6912v6913-2021-09-23) [Compare Source](https://togithub.com/netlify/cli/compare/v6.9.12...v6.9.13)

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