chore: CI upgrade golangci-lint

Author: temoto

.github/workflows/test.yaml

@@ -42,9 +42,9 @@ jobs:
       - uses: actions/setup-go@v6
         with:
           go-version: stable
-      - uses: golangci/golangci-lint-action@v8
+      - uses: golangci/golangci-lint-action@v9
         with:
-          version: v2.5.0
+          version: v2.6
 
   test:
     name: "test with Go ${{ matrix.go }}"