Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/main.yml

@@ -20,7 +20,7 @@ jobs:
           - '3.4.7'
 
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@v7
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:

.github/workflows/release.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       # Set up
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with: