Bump actions/checkout from 2 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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/apigee-release-pipeline.yml

@@ -17,7 +17,7 @@ jobs:
       PROXYGEN_API_NAME: hello-world
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/continous-integration-workflow.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0  # This causes all history to be fetched, which is required for calculate-version to function	
 

.github/workflows/sbom.yml

@@ -24,7 +24,7 @@ jobs:
       contents: write
     steps:
       - name: Checkout
-        uses: actions/checkout@v5        
+        uses: actions/checkout@v6        
 
       - name: Setup Python 3.13
         uses: actions/setup-python@v5

.github/workflows/spec-release-pipeline.yml

@@ -17,7 +17,7 @@ jobs:
       PROXYGEN_API_NAME: hello-world
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0