Bump actions/checkout from 4 to 6 (#153)

Author: dependabot[bot]

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
   build: # make sure build/ci work properly
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: actions/setup-node@v4
       with:
         node-version: '24.x'
@@ -19,7 +19,7 @@ jobs:
   test: # make sure the action works on a clean machine without building
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - uses: actions/setup-node@v4
       with:
         node-version: '24.x'