Update actions/checkout action to v6 (#44)

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

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -36,7 +36,7 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install tox & uv
         run: |
           pipx install tox
@@ -50,7 +50,7 @@ jobs:
     timeout-minutes: 5
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install tox & uv
         run: |
           pipx install tox

.github/workflows/release.yaml

@@ -26,7 +26,7 @@ jobs:
       VERSION: ${{ steps.export.outputs.VERSION }}
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: "Install uv"
@@ -54,7 +54,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: "Checkout"
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: "Download all the dists"
         uses: actions/download-artifact@v6
         with: