ci: bump actions/checkout from 4 to 5 (strands-agents#711)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/integration-test.yml

@@ -52,7 +52,7 @@ jobs:
          aws-region: us-east-1
          mask-aws-account-id: true
       - name: Checkout head commit
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           ref: ${{ github.event.pull_request.head.sha }} # Pull the commit from the forked repo
           persist-credentials: false  # Don't persist credentials for subsequent actions

.github/workflows/pypi-publish-on-release.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
       with:
         persist-credentials: false
 

.github/workflows/test-lint.yml

@@ -51,7 +51,7 @@ jobs:
       LOG_LEVEL: DEBUG
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           ref: ${{ inputs.ref }}  # Explicitly define which commit to check out
           persist-credentials: false  # Don't persist credentials for subsequent actions
@@ -73,7 +73,7 @@ jobs:
       contents: read
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           ref: ${{ inputs.ref }}
           persist-credentials: false