CI: update cache action to v4

Author: LaurentRDC

.github/workflows/ci.yml

@@ -28,19 +28,19 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       if: startsWith(runner.os, 'Linux')
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-${{ hashFiles('pyproject.toml') }}
 
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       if: startsWith(runner.os, 'macOS')
       with:
         path: ~/Library/Caches/pip
         key: ${{ runner.os }}-pip-${{ hashFiles('pyproject.toml') }}
 
-    - uses: actions/cache@v2
+    - uses: actions/cache@v4
       if: startsWith(runner.os, 'Windows')
       with:
         path: ~\AppData\Local\pip\Cache