chore(internal): update actions/checkout version

Author: stainless-app[bot]

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Java
         uses: actions/setup-java@v4
@@ -47,7 +47,7 @@ jobs:
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Java
         uses: actions/setup-java@v4
@@ -85,7 +85,7 @@ jobs:
     runs-on: ${{ github.repository == 'stainless-sdks/lithic-java' && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Java
         uses: actions/setup-java@v4

.github/workflows/publish-sonatype.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Java
         uses: actions/setup-java@v4

.github/workflows/release-doctor.yml

@@ -12,7 +12,7 @@ jobs:
     if: github.repository == 'lithic-com/lithic-java' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch' || startsWith(github.head_ref, 'release-please') || github.head_ref == 'next')
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Check release environment
         run: |