Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/rust.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
     - name: Build
       run: cargo build --verbose
     - name: Run tests