ci: bump golangci-lint action version and pin action version

- Update golangci-lint GitHub Action from v7 to v8 and specify version v2.1 instead of latest

Signed-off-by: appleboy <[email protected]>

Author: appleboy

.github/workflows/testing.yml

@@ -28,9 +28,9 @@ jobs:
           go-version-file: go.mod
           check-latest: true
       - name: Setup golangci-lint
-        uses: golangci/golangci-lint-action@v7
+        uses: golangci/golangci-lint-action@v8
         with:
-          version: latest
+          version: v2.1
           args: --verbose
       - uses: hadolint/[email protected]
         name: hadolint for Dockerfile