golangci-lint disable unused checks

[ivan-savciuc]

Disable golangci-lint unused checks.

Motivation:
Aiven in-house Jenkins build job fails from time to time with the following error:

golangci-lint run  -D errcheck --no-config --issues-exit-code=0 ./...
level=warning msg="[runner] Can't run linter goanalysis_metalinter: fact_deprecated: failed prerequisites: [email protected]/hashicorp/go-plugin"
level=error msg="Running error: fact_deprecated: failed prerequisites: [email protected]/hashicorp/go-plugin"

It looks like it is somehow related to these issues:

• Sporadic "Can't run linter goanalysis_metalinter: findcall: analysis skipped:" error on a cold cache golangci/golangci-lint#885
• Can't run linter goanalysis_metalinter: failed prerequisites golangci/golangci-lint#827

And the remedy for this problem could be to temporary disable unused checks.