Bump actions/checkout from 2 to 4 (#821)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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/master-codecov.yml

@@ -7,7 +7,7 @@ jobs:
     name: Run codecov on master
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: olafurpg/setup-scala@v14
         with:
           java-version: [email protected]

.github/workflows/master-release.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'scapegoat-scala/scapegoat'
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: git fetch --prune --unshallow
       - uses: olafurpg/setup-scala@v14
         with:

.github/workflows/pr-checks.yml

@@ -15,7 +15,7 @@ jobs:
           - 2.13.11
           - 2.13.12
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: olafurpg/setup-scala@v14
         with:
           java-version: adopt@1.${{matrix.java}}
@@ -34,7 +34,7 @@ jobs:
     name: Run additional checks
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: olafurpg/setup-scala@v14
         with:
           java-version: [email protected]