Use actions/checkout version 3

https://github.com/actions/checkout/releases/tag/v3.0.0

Author: koic

.github/workflows/spell_checking.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         python-version: [3.8]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v2
         with:
@@ -26,7 +26,7 @@ jobs:
     name: Check spelling with misspell
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install
         run: wget -O - -q https://git.io/misspell | sh -s -- -b .
       - name: Misspell