upgrade actions/checkout and actions/setup-dotnet

Author: JacksonTian

.github/workflows/ci.yml

@@ -12,9 +12,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Setup .NET Core
-      uses: actions/setup-dotnet@v1
+      uses: actions/setup-dotnet@v2
       with:
         dotnet-version: '2.x'
     - name: install altcover