Update voxmedia/github-action-slack-notify-build action to v2

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
voxmedia/github-action-slack-notify-build	action	major	v1 -> v2

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Release Notes

voxmedia/github-action-slack-notify-build

### [`v2`](https://togithub.com/voxmedia/github-action-slack-notify-build/compare/v1...v2) [Compare Source](https://togithub.com/voxmedia/github-action-slack-notify-build/compare/v1...v2)

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Renovate configuration

:date: Schedule: At any time (no schedule defined).

:vertical_traffic_light: Automerge: Disabled by config. Please merge this manually once you are satisfied.

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

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

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

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

[coveralls]

Pull Request Test Coverage Report for Build 634404651

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 86.628%

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Totals
Change from base Build 634399517:	0.0%
Covered Lines:	149
Relevant Lines:	172

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💛 - Coveralls