Bump GitHub Actions dependencies in sync workflow

- Update actions/checkout from v4 to v6
- Update actions/cache from v4 to v5

Author: gitctrlx

.github/workflows/sync.yml

@@ -26,11 +26,11 @@ jobs:
     timeout-minutes: 30
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: dtolnay/rust-toolchain@stable
 
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry/index