Bump actions/checkout from 3 to 4 (#194)

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>

.github/workflows/maven.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       # Use Java 8 to compile old Spigot version
       - uses: actions/setup-java@v3
@@ -79,7 +79,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Extract version from the pom.xml and compare to docs/version.txt
         id: version_diff  # Outputs 'same' or 'diff'
         run: mkdir -p docs && echo $(grep --max-count=1 '<version>' pom.xml | awk -F '>' '{ print $2 }' | awk -F '<' '{ print $1 }') >> docs/version_new.txt && diff -q --ignore-space-change --strip-trailing-cr --ignore-blank-lines docs/version.txt docs/version_new.txt 2>&1 && echo "result=same" >> $GITHUB_OUTPUT || echo "result=diff" >> $GITHUB_OUTPUT