Upgrade actions/cache to v4

Author: marijnh

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
     steps:
       - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac #v4.0.0
 
-      - uses: actions/cache@704facf57e6136b1bc63b828d79edcd491f0ee84 #v3.3.2
+      - uses: actions/cache@v4
         with:
           path: '/home/runner/work/codemirror/codemirror5/node_modules'
           key: ${{ runner.os }}-modules