updating caching version

Author: JTorgander

.github/workflows/posteriordb_content.yml

@@ -34,7 +34,7 @@ jobs:
 
       - name: Cache R packages
         if: runner.os != 'Windows'
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ env.R_LIBS_USER }}
           key: ${{ runner.os }}-r-${{ matrix.config.r }}-${{ hashFiles('DESCRIPTION') }}