Bump actions/cache from 3 to 4 (#227)

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

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

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

.github/workflows/ci-format.yml

@@ -17,7 +17,7 @@ jobs:
       with:
         python-version: '3.10'
     - name: Restore stats
-      uses: actions/cache/restore@v3
+      uses: actions/cache/restore@v4
       with:
         key: reviewer-stats-${{ github.run_id }}
         restore-keys: |

.github/workflows/sphinx-check-links.yml

@@ -35,7 +35,7 @@ jobs:
     - name: Install doxygen and graphviz
       run: sudo apt-get install -y doxygen graphviz
     - name: Restore stats
-      uses: actions/cache/restore@v3
+      uses: actions/cache/restore@v4
       with:
         key: reviewer-stats-${{ github.run_id }}
         restore-keys: |

.github/workflows/sphinx-check-warnings-pr.yml

@@ -27,7 +27,7 @@ jobs:
         python -m pip install .
       shell: bash
     - name: Restore stats
-      uses: actions/cache/restore@v3
+      uses: actions/cache/restore@v4
       with:
         key: reviewer-stats-${{ github.run_id }}
         restore-keys: |

.github/workflows/sphinx-check-warnings.yml

@@ -32,7 +32,7 @@ jobs:
         python -m pip install .
       shell: bash
     - name: Restore stats
-      uses: actions/cache/restore@v3
+      uses: actions/cache/restore@v4
       with:
         key: reviewer-stats-${{ github.run_id }}
         restore-keys: |