fix(ci): use internal make target inside container job

CI check job already runs inside the dev-toolchain container,
so call _check directly instead of check which tries to spawn
Docker-in-Docker.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: matthew-on-git

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
       image: ghcr.io/devrail-dev/dev-toolchain:v1
     steps:
       - uses: actions/checkout@v4
-      - run: make check
+      - run: make _check
 
   build:
     runs-on: ubuntu-latest