Update actions/checkout action to v2 (#423)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
 
       - name: Get yarn cache directory path
         id: yarn-cache-dir
@@ -40,7 +40,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
 
       - name: Get yarn cache directory path
         id: yarn-cache-dir
@@ -68,7 +68,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
 
       - name: Get yarn cache directory path
         id: yarn-cache-dir