Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/check-code-style.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # brew install sbt; cd graphql-java-codegen-sbt-plugin; sbt fmt or sbt check
       - name: Check Scala Code Style

.github/workflows/github.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         jdk-version: [ 8, 11, 17 ]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Java ${{ matrix.jdk-version }}
         uses: actions/setup-java@v4
@@ -84,7 +84,7 @@ jobs:
     if: github.event_name != 'pull_request'    
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
          fetch-depth: 0
       - name: Setup Java

.github/workflows/release.yml

@@ -32,7 +32,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           ref: ${{ github.event.inputs.release_branch }}
 

.github/workflows/update-version.yml

@@ -11,7 +11,7 @@ jobs:
   update-version:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Update version of Maven plugin sub-project
         working-directory: plugins/maven/graphql-java-codegen-maven-plugin