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](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>

Author: dependabot[bot]

.github/workflows/performance.yml

@@ -30,7 +30,7 @@ jobs:
         echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
         echo "dir=$(pip cache dir)" >> $env:GITHUB_OUTPUT
     - name: pip cache
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         path: ${{ steps.pip-cache.outputs.dir }}
         key: py${{ matrix.python-version }}-${{ matrix.os }}-pip

.github/workflows/pythontests.yml

@@ -34,7 +34,7 @@ jobs:
         python -m pip install -U pip # to ensure version > 20 to have cache dir
         echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
     - name: pip cache
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         path: ${{ steps.pip-cache.outputs.dir }}
         key: py${{ matrix.python-version }}-${{ matrix.os }}-pip