actually lint file on CI (#2018)

* replace deprecated golangci-lint output format

CI was producing this kind of messages:
> [config_reader] The output format `github-actions` is deprecated, please use `colored-line-number`

* Actually lint files on CI

.github/workflows/lint.yml

@@ -31,7 +31,7 @@ jobs:
 
       - name: golangci-lint
         if: steps.changed-files.outputs.files == 'true'
-        run: nix develop --command -- golangci-lint run --new-from-rev=${{github.event.pull_request.base.sha}} --out-format=github-actions .
+        run: nix develop --command -- golangci-lint run --new-from-rev=${{github.event.pull_request.base.sha}} --out-format=colored-line-number
 
   prettier-lint:
     runs-on: ubuntu-latest