Update actions/checkout from 2 to 3 (#5)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/tests.yml

@@ -73,7 +73,7 @@ jobs:
         run: |
           apt update && apt-get install git -yqq
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: install dependencies
         run: |
           composer require --no-update silverstripe/recipe-cms:$RECIPE_CMS_VERSION &&\
@@ -118,7 +118,7 @@ jobs:
         run: |
           apt update && apt-get install git -yqq
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: install dependencies
         run: |
           composer require --no-update silverstripe/recipe-cms:$RECIPE_CMS_VERSION &&\
@@ -130,7 +130,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: lint source
         uses: chindit/actions-phpcs@master
         with: