Bump actions/cache from 5 to 6

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](https://github.com/actions/cache/compare/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>

.github/workflows/desktop-build.yml

@@ -162,7 +162,7 @@ jobs:
 
       - name: "Restore compiler cache (ccache)"
         id: ccache_restore
-        uses: actions/cache/restore@v5
+        uses: actions/cache/restore@v6
         env:
           BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
         with:
@@ -215,7 +215,7 @@ jobs:
 
       - name: "Save updated compiler cache (ccache)"
         if: github.ref == 'refs/heads/master'
-        uses: actions/cache/save@v5
+        uses: actions/cache/save@v6
         with:
           key: ${{ steps.ccache_restore.outputs.cache-primary-key }}
           path: ${{ env.CACHE }}
@@ -365,7 +365,7 @@ jobs:
       - name: "[macOS] Restore compiler cache (ccache)"
         if: matrix.os == 'macOS' && matrix.use_ccache == 1
         id: ccache_restore
-        uses: actions/cache/restore@v5
+        uses: actions/cache/restore@v6
         env:
           BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
         with:
@@ -387,7 +387,7 @@ jobs:
       - name: "[macOS] Restore thin Qt ${{ steps.resolve_qt_version.outputs.version }} libraries"
         if: matrix.os == 'macOS'
         id: restore_qt
-        uses: actions/cache/restore@v5
+        uses: actions/cache/restore@v6
         with:
           key: thin-qt-macos-${{ matrix.soc }}-${{ steps.resolve_qt_version.outputs.version }}
           path: ${{ github.workspace }}/Qt
@@ -410,7 +410,7 @@ jobs:
 
       - name: "[macOS] Cache thin Qt libraries"
         if: matrix.os == 'macOS' && steps.restore_qt.outputs.cache-hit != 'true'
-        uses: actions/cache/save@v5
+        uses: actions/cache/save@v6
         with:
           key: thin-qt-macos-${{ matrix.soc }}-${{ steps.resolve_qt_version.outputs.version }}
           path: ${{ github.workspace }}/Qt
@@ -473,7 +473,7 @@ jobs:
 
       - name: "[macOS] Save updated compiler cache (ccache)"
         if: matrix.os == 'macOS' && matrix.use_ccache == 1 && github.ref == 'refs/heads/master'
-        uses: actions/cache/save@v5
+        uses: actions/cache/save@v6
         with:
           key: ${{ steps.ccache_restore.outputs.cache-primary-key }}
           path: ${{ env.CCACHE_DIR }}