CONTRIBUTING.md: linter section links to removed .golangci.yml

The "Running the linter" section in CONTRIBUTING.md is out of date since #6380 moved the lint config to grafana/k6-ci.

It currently says:

The actual version you can find in our .golangci.yml. To run it locally, first install it, then run: make lint

Two things are off:

1. The .golangci.yml link returns a 404. That file was removed in #6380 and the repo now only has .golangci.patch.
2. You don't need to install golangci-lint anymore. make lint downloads the base config from grafana/k6-ci into build/lint/, applies .golangci.patch, and runs go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@<version>, with the version taken from the first line of that base config (currently v2.13.2). I ran it locally without golangci-lint installed and it worked.

So someone following the guide hits a dead link, and may install a golangci-lint version that doesn't match what CI uses.

Suggested wording:

We use golangci-lint to lint the code in CI. The config comes from grafana/k6-ci, with k6-specific changes in .golangci.patch. To run it locally with the same version as CI:

bash复制

make lint

If you need to change the lint config, edit build/lint/.golangci.yml after running make lint, then run make update-lint-patch to regenerate the patch.

I can open a PR for this.