chore(deps): bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/main.yaml

@@ -36,7 +36,7 @@ jobs:
 
     steps:
       - name: 📚 Git Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: 🎯 Setup Dart
         uses: dart-lang/setup-dart@v1

.github/workflows/pub_publish.yaml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 📚 Git Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: 🎯 Setup Dart
         uses: dart-lang/setup-dart@v1
       - name: 🐦 Setup Flutter

.github/workflows/sync_labels.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: ⤵️ Check out code from GitHub
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: 🚀 Run Label Sync
         uses: srealmoreno/label-sync-action@v2