Bump the actions group across 1 directory with 2 updates

Bumps the actions group with 2 updates in the / directory: [actions/checkout](https://github.com/actions/checkout) and [actions/cache](https://github.com/actions/cache).


Updates `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)

Updates `actions/cache` from 4 to 5
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
- dependency-name: actions/cache
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -23,7 +23,7 @@ jobs:
     outputs:
       triggered: ${{ steps.detect-trigger.outputs.trigger-found }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
@@ -52,7 +52,7 @@ jobs:
         python-version: ["3.11", "3.13"]
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
@@ -79,7 +79,7 @@ jobs:
           python -c 'import xarray_array_testing'
 
       - name: Restore cached hypothesis directory
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v5
         with:
           path: .hypothesis/
           key: cache-hypothesis
@@ -89,7 +89,7 @@ jobs:
           python -m pytest --cov=xarray_array_testing
 
       - name: Cache hypothesis directory
-        uses: actions/cache/save@v4
+        uses: actions/cache/save@v5
         with:
           path: .hypothesis/
           key: cache-hypothesis