set actions/cache to v4

Author: LiNk-NY

.github/workflows/pr_check.yml

@@ -31,7 +31,7 @@ jobs:
 
       - name: Cache R packages
         if: runner.os != 'Windows'
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: /usr/local/lib/R/site-library
           key: ${{ runner.os }}-r-1-${{ hashFiles('.github/depends.Rds') }}