chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build_grpc.yaml

@@ -21,7 +21,7 @@ jobs:
         python_version: [3.9, 3.12, 3.13]
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3

.github/workflows/main.yaml

@@ -14,7 +14,7 @@ jobs:
       current-release: ${{ steps.current.outputs.CURRENT_RELEASE }}
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Install dependencies
         run: |