Update GitHub Actions to latest versions

- actions/checkout: v2/v3 → v4
- docker/setup-buildx-action: v2 → v3
- docker/build-push-action: v2 → v6

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: nindanaoto

.github/workflows/benchmark.yml

@@ -10,12 +10,12 @@ jobs:
     runs-on: Ubuntu-22.04
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
 
     - name: Set up Buildx
-      uses: docker/setup-buildx-action@v2
+      uses: docker/setup-buildx-action@v3
 
-    - uses: docker/build-push-action@v2
+    - uses: docker/build-push-action@v6
       with:
         file: Dockerfile
         tags: tfhepp-2204

.github/workflows/test.yml

@@ -10,12 +10,12 @@ jobs:
     runs-on: Ubuntu-22.04
     steps:
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Set up Buildx
-      uses: docker/setup-buildx-action@v2
+      uses: docker/setup-buildx-action@v3
 
-    - uses: docker/build-push-action@v2
+    - uses: docker/build-push-action@v6
       with:
         file: Dockerfile
         tags: tfhepp-2204