[ci] Update actions/checkout action to v6

Author: lpinca

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
             node: 22
             os: windows-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: ${{ matrix.node }}
@@ -55,7 +55,7 @@ jobs:
           - arch: x86
             os: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 20
@@ -76,7 +76,7 @@ jobs:
       contents: write # Needed for softprops/action-gh-release.
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/download-artifact@v6
         with:
           path: prebuilds