Update wpcs.yml

Bump actions/checkout version.

Author: B-Interactive

.github/workflows/wpcs.yml

@@ -12,7 +12,7 @@ jobs:
       name: WPCS
       runs-on: ubuntu-latest
       steps:
-        - uses: actions/checkout@v2
+        - uses: actions/checkout@v4
         - name: WPCS check
           uses: 10up/wpcs-action@stable
           with: