upgrade to actions/cache@v3

Author: Atry

.github/workflows/gh-pages.yml

@@ -32,7 +32,7 @@ jobs:
       with:
         node-version: "${{ steps.nodenv.outputs.node-version }}"
     - name: Cache SBT
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: | 
           ~/.ivy2/local/