fix #12666: vue.d.ts: Relativise to v3-component-public-instance

[sandersn]

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 main branch for v2.x (or to a previous version branch), not the master 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/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

Other information:

I didn't investigate why vue's tsconfig incorrectly resolves an absolute reference to v3-component-public-instance, so I was unable to start with a failing test.

[sandersn]

The setting that allows types/tsconfig.json to resolve absolute references by mistake is baseUrl: ".". I removed it, because I don't think it makes sense here.