Bump actions/checkout to v3

Author: mfussenegger

.github/workflows/linter.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Lint Code Base
         uses: github/super-linter/slim@v4

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
         neovim_version: ['nightly']
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - run: date +%F > todays-date
       - name: Restore cache for today's nightly.
         uses: actions/cache@v2