Bump Documenter workflow checkout action

Author: ReubenJ

.github/workflows/Documenter.yml

@@ -10,7 +10,7 @@ jobs:
     name: Documentation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest
         env: