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

Author: renovate[bot]

.github/workflows/deploy.yml

@@ -14,7 +14,7 @@ jobs:
     timeout-minutes: 5
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       # Slack CLI は Deno ランタイムを必要とします
       - name: Install Deno runtime

.github/workflows/test.yaml

@@ -13,7 +13,7 @@ jobs:
     timeout-minutes: 300
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0 # Shallow clones should be disabled for a better relevancy of analysis
       - uses: denoland/setup-deno@v1