Update actions/checkout digest to b4ffde6

Author: renovate[bot]

.github/workflows/rake.yml

@@ -16,7 +16,7 @@ jobs:
         ruby: [2.7, 3.1]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}