Update action/cache from v2 to v4

cache v2 已不被支援。现更新至v4。看起来不需要更改其他东西。

Author: SodaWithoutSparkles

.github/workflows/build.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Get yarn cache directory path
         id: yarn-cache-dir-path
         run: echo "dir=$(yarn cache dir)" >> $GITHUB_OUTPUT
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         id: yarn-cache
         with:
           path: ${{ steps.yarn-cache-dir-path.outputs.dir }}