Replace forked cache by official npm (#21)

* Replace forked cache by official npm

* Follow the same validation as @action/cache

* Remove debug log

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
   build: # make sure build/ci work properly
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - run: |
         npm install
         npm run prepare-deps
@@ -18,7 +18,7 @@ jobs:
   test: # make sure the action works on a clean machine without building
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - uses: ./
       with:
         version: v1.26