Update actions/checkout action to v5 (#17)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
         os: ["ubuntu", "macos", "windows"]
         ruby: ["3.2", "3.3", "3.4"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
         with:
           submodules: true
       - uses: ruby/setup-ruby@v1

.github/workflows/doc.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ruby