build(deps): bump actions/cache from 5 to 6 (#810)

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5...v6)

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

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

Author: dependabot[bot]

.github/workflows/pull_request.yml

@@ -281,7 +281,7 @@ jobs:
       - name: Prepare CI Environment
         uses: ./.github/actions/prepare_env
       - name: Cache sample .build
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         continue-on-error: true
         with:
           path: Samples/${{ matrix.sample_app }}/.build
@@ -320,7 +320,7 @@ jobs:
         env:
           SWIFT_VERSION: "${{ matrix.swift_version }}"
       - name: Cache sample .build
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         continue-on-error: true
         with:
           path: Samples/${{ matrix.sample_app }}/.build