Bump actions/checkout from 3 to 4 (#154)

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

Author: dependabot[bot]

.github/workflows/testing.yml

@@ -18,7 +18,7 @@ jobs:
         go: [ '1.21', '1.20' ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}
@@ -35,7 +35,7 @@ jobs:
         go: [ '1.21', '1.20' ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}
@@ -51,7 +51,7 @@ jobs:
         go: [ '1.21', '1.20' ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}
@@ -71,7 +71,7 @@ jobs:
         go: [ '1.21', '1.20' ]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}