Bump actions/checkout to v4

Author: graygilmore

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ jobs:
     name: Lighthouse
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Lighthouse
         uses: shopify/lighthouse-ci-action@v1
         with:
@@ -19,7 +19,7 @@ jobs:
     name: Theme Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Theme Check
         uses: shopify/theme-check-action@v2
         with: