chore(deps): update actions/checkout action to v6 (#31)

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

Author: renovate[bot]

.github/workflows/release-please.yml

@@ -29,7 +29,7 @@ jobs:
       # don't trigger additional workflows.
       - name: Checkout
         if: steps.rp.outputs.release_created == 'true'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup Node
         if: steps.rp.outputs.release_created == 'true'

.github/workflows/release.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.inputs.ref || github.ref }}