Activate lint staticcheck.

api/internal/accumulator/refvartransformer.go

@@ -70,6 +70,7 @@ func (rv *refVarTransformer) replaceVars(in interface{}) (interface{}, error) {
 		// This field can potentially contain a $(VAR) since it is
 		// of string type.
 		return expansion2.Expand(s, rv.mappingFunc), nil
+	//nolint:staticcheck (erroneously claims that `case nil` is unreachable)
 	case nil:
 		return nil, nil
 	default: