Bump actions/checkout from 3 to 4

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] <support@github.com>

.github/workflows/apidiff.yaml

@@ -16,12 +16,12 @@ jobs:
       - name: Install dependencies
         run: GO111MODULE=off go get golang.org/x/exp/cmd/apidiff
       - name: Checkout old code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: ${{ github.base_ref }}
           path: "old"
       - name: Checkout new code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: "new"
       - name: APIDiff

.github/workflows/lint.yaml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Lint
         uses: golangci/golangci-lint-action@v3
         with:

.github/workflows/tests.yaml

@@ -15,7 +15,7 @@ jobs:
       with:
         go-version: ${{ matrix.go-version }}
     - name: Checkout code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Build
       run: go build -v ./...
     - name: Test