Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install Node
         uses: actions/setup-node@v2
         with:
@@ -36,7 +36,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-node@v2
         with:
           node-version: 12.x
@@ -65,7 +65,7 @@ jobs:
           - embroider-optimized
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install Node
         uses: actions/setup-node@v2
         with: