chore: return to typescript v6.x

[Tony133]

Proposal:

I updated the TypeScript dependency to version 6.x, because dependabot had updated the TypeScript dependency version to version 7.x, but this caused an error in lint since eslint v9 and neostandard are not compatible yet, making the pipeline red.
Despite the CI being red, see here: 4858419 and https://github.com/fastify/busboy/actions/runs/29655747873/job/88109667826#step:5:1 dependabot merged the PR automatically.

Currently, major or automated updates to TypeScript can introduce breaking changes or type mismatches with our current linting setup (specifically with eslint, neostandard, and related plugins like ts-api-utils), causing commands like npm run lint:fix to fail with runtime type errors.

By ignoring it for now, we ensure that TypeScript updates are handled manually and verified alongside the rest of the linting toolchain.

cc @fastify/leads @fastify/libraries

[climba03003]

I would say that we should update the shared workflows to ensure the linter fail do not trigger merging.

[Tony133]

I would say that we should update the shared workflows to ensure the linter fail do not trigger merging.

Yes, I agree 😉👍🏻

let's hope neostandard becomes compatible with eslint v10.x soon, we are a bit "stuck" at the moment 😄

[mcollina]

lgtm