ci: fix go lint error from latest golangci-lint release (#2020)

## Summary of Changes
- Fix Go [lint
error](https://github.com/malbeclabs/doublezero/actions/runs/18972310051/job/54182918267?pr=2018)
that started happening after the latest (v2.6.0) version of
`golangci-lint` was released a couple days ago
- The error complains about the use of `// +build !linux` but even if
you remove that it continues to complain about it, that rule is excluded
via `.golanci.yaml` instead
- This error is currently causing all CI runs or use of `make go-lint`
to
[fail](https://github.com/malbeclabs/doublezero/actions/runs/18972310051/job/54182918267?pr=2018)

## Testing Verification
- Error is reproduceable locally if you upgrade to latest golanci-lint
version (or rebuild devcontainer) and run `make go-lint`, and no longer
happens after this change

Author: snormore

.golangci.yaml

@@ -74,6 +74,9 @@ linters:
       - third_party$
       - builtin$
       - examples$
+    rules:
+      - linters: [govet]
+        text: 'buildtag: \+build line is no longer needed'
 formatters:
   enable:
     - gofmt