Bump actions/cache from 2 to 4 (#44)

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v2...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/test_suite.yml

@@ -29,7 +29,7 @@ jobs:
       with:
         fetch-depth: 20
 
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       with:
         path: ~/.cache/pip
         key: ${{ hashFiles('setup.py') }}-py${{ matrix.python-version }}
@@ -66,7 +66,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cache
         key: ${{ runner.os }}-${{ matrix.python-version }}-ci-quality
@@ -102,7 +102,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Cache
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cache
         key: ${{ runner.os }}-${{ matrix.python-version }}-ci-docs