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

Author: renovate[bot]

.github/workflows/publish.yml

@@ -16,7 +16,7 @@ jobs:
       name: crates.io
       url: https://crates.io/crates/rustpython-unparser
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Publish
         run: cargo publish
         env:

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Build
         run: cargo build --verbose
       - name: Run tests