Bump actions/checkout from 4 to 6 (#99)

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/ci.yml

@@ -41,7 +41,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python 3.10
         uses: actions/setup-python@v6
@@ -59,7 +59,7 @@ jobs:
       id-token: write
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python 3.10
         uses: actions/setup-python@v6
@@ -101,7 +101,7 @@ jobs:
       labs: ${{ steps.discover.outputs.labs }}
     steps:
       - name: Checkout lab-validation
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Discover available labs
         id: discover
@@ -117,7 +117,7 @@ jobs:
     if: inputs.batfish_docker == ''
     steps:
       - name: Checkout Batfish
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: batfish/batfish
           path: batfish
@@ -167,7 +167,7 @@ jobs:
 
     steps:
       - name: Checkout lab-validation
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: lab-validation
 

.github/workflows/reusable-lab-validation.yml

@@ -48,7 +48,7 @@ jobs:
       labs: ${{ steps.discover.outputs.labs }}
     steps:
       - name: Checkout lab-validation
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: batfish/lab-validation
 
@@ -71,7 +71,7 @@ jobs:
     if: inputs.batfish_docker == ''
     steps:
       - name: Checkout Batfish
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ${{ inputs.batfish_repository || 'batfish/batfish' }}
           path: batfish
@@ -121,7 +121,7 @@ jobs:
 
     steps:
       - name: Checkout lab-validation
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: batfish/lab-validation
           path: lab-validation