Bump actions/checkout from 4 to 5 (#108)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to
5.

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/unit-test.yml

@@ -14,7 +14,7 @@ jobs:
         os: [ 'ubuntu-latest', 'macOS-latest', 'windows-latest' ]
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}