simplify CI to docker build only (refs #130)

The Dockerfile already runs make check, so the CI action only needs
to run docker build. Remove go setup, linter installation, and
direct make check invocation from the workflow.

.gitea/workflows/check.yml

@@ -10,7 +10,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4, 2024-10-13
 
-      - name: Build (runs make check via Dockerfile)
+      - name: Build (runs make check inside Dockerfile)
         run: docker build .