Bump checkout action to v4

Author: bwestover

.github/workflows/test.yaml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'push' || github.event_name == 'pull_request'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run action (no inputs expected)
         uses: ./
         id: print_inputs
@@ -41,7 +41,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'workflow_dispatch'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run action (inputs expected)
         uses: ./
         id: print_inputs
@@ -63,7 +63,7 @@ jobs:
   test-env-vars:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run action (with env vars)
         uses: ./
         id: print_inputs_and_env