Upgrade: [dependabot] - bump actions/checkout from 4 to 6

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/release_psu_to_ref.yml

@@ -21,7 +21,7 @@ jobs:
           echo "## psuWorkflowRunID : [${{ github.event.inputs.psuWorkflowRunID }}](https://github.com/NHSDigital/eps-prescription-status-update-api/actions/runs/${{ github.event.inputs.psuWorkflowRunID }})" >> "$GITHUB_STEP_SUMMARY"
 
       - name: Checkout local github actions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ env.BRANCH_NAME }}
           fetch-depth: 0

.github/workflows/run_cpsu_load.yml

@@ -42,7 +42,7 @@ jobs:
           echo "## maxVusers : ${{ github.event.inputs.maxVusers }}" >> "$GITHUB_STEP_SUMMARY"
 
       - name: Checkout repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ env.BRANCH_NAME }}
 

.github/workflows/run_notify_load.yml

@@ -51,7 +51,7 @@ jobs:
           fi
 
       - name: Checkout repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ env.BRANCH_NAME }}
 

.github/workflows/run_psu_load.yml

@@ -42,7 +42,7 @@ jobs:
           echo "## maxVusers : ${{ github.event.inputs.maxVusers }}" >> "$GITHUB_STEP_SUMMARY"
 
       - name: Checkout repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ env.BRANCH_NAME }}