⬆️ Update dependency execa to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
execa	dependencies	major	^3.0.0 -> ^4.0.0

---

Release Notes

sindresorhus/execa

### [`v4.0.0`](https://togithub.com/sindresorhus/execa/releases/v4.0.0) [Compare Source](https://togithub.com/sindresorhus/execa/compare/v3.4.0...v4.0.0) #### Breaking changes - Require Node.js 10 ([`5a9c76f`](https://togithub.com/sindresorhus/execa/commit/5a9c76f)) - Add `stderr` and `stdout` to [`error.message`](https://togithub.com/sindresorhus/execa#message). A new property [`error.shortMessage`](https://togithub.com/sindresorhus/execa#shortmessage) is now available to retrieve the error message without `stderr` nor `stdout` ([#​397](https://togithub.com/sindresorhus/execa/issues/397)) #### Bug fixes - Fix `childProcess.kill()` not working with Electron ([#​400](https://togithub.com/sindresorhus/execa/issues/400))

---

Renovate configuration

:date: Schedule: "before 3am on Monday" in timezone Asia/Tokyo.

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

:recycle: Rebasing: Whenever PR becomes conflicted, or if you modify the PR title to begin with "rebase!".

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

---

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

---

Newsflash: Renovate has joined WhiteSource, and is now free for all use. Learn more or view updated terms and privacy policies.