docs: fixes url of link to Vue3 version

[luckylooke]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch.
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue-test-utils/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

[netlify]

❌ Deploy Preview for vue-test-utils-v1 failed.

Name	Link
🔨 Latest commit	d51223e
🔍 Latest deploy log	https://app.netlify.com/sites/vue-test-utils-v1/deploys/63c7366d4ca94b0009befe05

[luckylooke]

I just want to fix docs, I have no clue what's wrong with pipeline, can somebody help? Pls 🙏

[lmiller1990]

I am not sure what's with the pipeline. I'll merge this and find out after.