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/deploy-docs.yml

@@ -16,7 +16,7 @@ jobs:
     # if: github.repository_owner == 'spring-cloud'
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           ref: docs-build
           fetch-depth: 1

.github/workflows/maven.yaml

@@ -27,7 +27,7 @@ jobs:
     steps:
 
       - name: checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: set env variables
         uses: ./.github/workflows/composites/env-variables
@@ -103,7 +103,7 @@ jobs:
     steps:
 
       - name: checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: clean space
         uses: ./.github/workflows/composites/clean-space
@@ -147,7 +147,7 @@ jobs:
     steps:
 
       - name: checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: clean space
         uses: ./.github/workflows/composites/clean-space
@@ -184,7 +184,7 @@ jobs:
     steps:
 
       - name: checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: compute and save running time of tests
         uses: ./.github/workflows/composites/test-times
@@ -196,7 +196,7 @@ jobs:
     steps:
 
       - name: checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: compute and save running time of tests
         uses: ./.github/workflows/composites/test-times