Update actions/checkout action to v4 (#118)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/bump.yml

@@ -18,7 +18,7 @@ jobs:
       run:
         working-directory: ./servant-swagger-ui-core
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Cache cabal store
         id: cache