Update actions/checkout action to v3

Author: renovate[bot]

.github/workflows/codecov.yml

@@ -8,7 +8,7 @@ jobs:
   codecov:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions/setup-ruby@v1
         with:
           ruby-version: 2.7

.github/workflows/rake.yml

@@ -16,7 +16,7 @@ jobs:
         ruby: [2.7]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}