Update dependency @vue/test-utils to v2.0.0-rc.21

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@vue/test-utils	2.0.0-rc.20 -> 2.0.0-rc.21

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Release Notes

vuejs/test-utils

### [`v2.0.0-rc.21`](https://togithub.com/vuejs/test-utils/releases/v2.0.0-rc.21) [Compare Source](https://togithub.com/vuejs/test-utils/compare/v2.0.0-rc.20...v2.0.0-rc.21) This is the final release candidate, unless something major comes up. We will move to 2.0.0 next release. - [chore: Bump vue 3.2.33](https://togithub.com/vuejs/test-utils/pull/1442) - [chore: Bump vue 3.2.33](https://togithub.com/vuejs/test-utils/pull/1442) - [chore: add test](https://togithub.com/vuejs/test-utils/pull/1441) - [fix: forward Ref prop on mount](https://togithub.com/vuejs/test-utils/commit/7059cff968bff33b9fc290fe77984afd3fc3f4b2) - [fix: disable stubs for built-in components on shallow](https://togithub.com/vuejs/test-utils/commit/eb8284530eacd36ce5435fccffe9d45a761b503f)

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