Update to actions/checkout@v2

Author: tianon

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     outputs:
       strategy: ${{ steps.generate-jobs.outputs.strategy }}
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - id: generate-jobs
         name: Generate Jobs
         run: |
@@ -33,7 +33,7 @@ jobs:
     name: ${{ matrix.name }}
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Prepare Environment
         run: ${{ matrix.runs.prepare }}
       - name: Pull Dependencies