Update module github.com/urfave/cli/v2 to v2.6.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
github.com/urfave/cli/v2	require	minor	v2.5.1 -> v2.6.0

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Release Notes

urfave/cli

### [`v2.6.0`](https://togithub.com/urfave/cli/releases/v2.6.0) [Compare Source](https://togithub.com/urfave/cli/compare/v2.5.1...v2.6.0) #### What's Changed - Simplified flag value access by [@​toaster](https://togithub.com/toaster) in [https://github.com/urfave/cli/pull/1367](https://togithub.com/urfave/cli/pull/1367) #### New Contributors - [@​toaster](https://togithub.com/toaster) made their first contribution in [https://github.com/urfave/cli/pull/1367](https://togithub.com/urfave/cli/pull/1367) **Full Changelog**: https://github.com/urfave/cli/compare/v2.5.1...v2.6.0

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