Skip cleanup on Windows

Author: liufengyun

.github/workflows/ci.yaml

@@ -102,12 +102,6 @@ jobs:
     container: lampepfl/dotty-windows:2020-10-02
 
     steps:
-      - name: Checkout cleanup script
-        uses: actions/checkout@v2
-
-      - name: Cleanup
-        bash: .github/workflows/cleanup.sh
-
       - name: Git Checkout
         uses: actions/checkout@v2
 
@@ -140,12 +134,6 @@ jobs:
     container: lampepfl/dotty-windows:2020-10-02
 
     steps:
-      - name: Checkout cleanup script
-        uses: actions/checkout@v2
-
-      - name: Cleanup
-        bash: .github/workflows/cleanup.sh
-
       - name: Git Checkout
         uses: actions/checkout@v2