Update devDependency @zeit/ncc to ^0.21.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
@zeit/ncc	devDependencies	patch	^0.21.0 -> ^0.21.1

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Release Notes

zeit/ncc

### [`v0.21.1`](https://togithub.com/zeit/ncc/releases/0.21.1) [Compare Source](https://togithub.com/zeit/ncc/compare/0.21.0...0.21.1) ##### Patches - Fix minified source-map outputs format: [#​504](https://togithub.com/zeit/ncc/issues/504) - Add Github Actions CI, remove Circle CI: [#​494](https://togithub.com/zeit/ncc/issues/494) - Bump npm from 6.9.0 to 6.13.4: [#​493](https://togithub.com/zeit/ncc/issues/493) ##### Credits Huge thanks to [@​legendecas](https://togithub.com/legendecas) for helping!

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