ci: attempt at fixing golangci's depguard

Created by: jhchabran

This is very empirical, and checking from where exactly this is coming from is a rabbithole. It seems that with golangci-lint 1.45, having updated depguard is coming with strange behaviour regarding the list-type.

After multiple manual attempts on the CI, I noticed that while we get the issues in https://buildkite.com/sourcegraph/sourcegraph/builds/138564#392cb37d-9228-43c6-a051-9a94c11b3657 with blacklist, it's not happening with `denylist. I was not able to reproduce it locally, which is very strange.

Test plan

green builds