Bump actions/checkout from 3 to 4 (#2811)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

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

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

.github/workflows/knative-dependabot.yaml

@@ -13,7 +13,7 @@ jobs:
     if: ${{ github.actor == 'dependabot[bot]' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: ${{ github.head_ref }}
           path: ./src/github.com/${{ github.repository }}

.github/workflows/knative-downstream.yaml

@@ -59,7 +59,7 @@ jobs:
         go install github.com/google/go-licenses@latest
 
     - name: Checkout upstream at ${{ github.base_ref }}
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         path: upstream
@@ -80,7 +80,7 @@ jobs:
          git pull --no-rebase --no-commit upstream ${{ github.base_ref }}
 
     - name: Checkout downstream at ${{ github.base_ref }}
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         ref: ${{ github.base_ref }}
         repository: ${{ matrix.repo }}