Bump actions/checkout from 3 to 4 (#31)

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/build.yaml

@@ -29,7 +29,7 @@ jobs:
     runs-on: ${{ matrix.platform.os }}
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           # Check https://github.com/livepeer/go-livepeer/pull/1891

.github/workflows/test.yaml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.sha }}
@@ -62,7 +62,7 @@ jobs:
 
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.sha }}