Bump actions/cache from 4 to 5

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5.
- [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/v4...v5)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build_offline_docs.yml

@@ -34,7 +34,7 @@ jobs:
           echo "PYTHON_VERSION=$(python --version)" >> $GITHUB_OUTPUT
 
       - name: Restore cached virtualenv
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v5
         with:
           key: venv-${{ runner.os }}-${{ steps.pythonv.outputs.PYTHON_VERSION }}-${{ hashFiles('requirements.txt') }}
           path: .venv
@@ -50,7 +50,7 @@ jobs:
           sudo apt install parallel libwebp7 imagemagick
 
       - name: Save virtualenv cache
-        uses: actions/cache/save@v4
+        uses: actions/cache/save@v5
         with:
           key: venv-${{ runner.os }}-${{ steps.pythonv.outputs.PYTHON_VERSION }}-${{ hashFiles('requirements.txt') }}
           path: .venv

.github/workflows/check_urls.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v5
 
       - name: Restore lychee cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: .lycheecache
           key: cache-lychee-${{ github.sha }}

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
           echo "PYTHON_VERSION=$(python --version)" >> $GITHUB_OUTPUT
 
       - name: Restore cached virtualenv
-        uses: actions/cache/restore@v4
+        uses: actions/cache/restore@v5
         with:
           key: venv-${{ runner.os }}-${{ steps.pythonv.outputs.PYTHON_VERSION }}-${{ hashFiles('requirements.txt') }}
           path: .venv
@@ -43,7 +43,7 @@ jobs:
           echo "VIRTUAL_ENV=$VIRTUAL_ENV" >> $GITHUB_ENV
 
       - name: Save virtualenv cache
-        uses: actions/cache/save@v4
+        uses: actions/cache/save@v5
         with:
           key: venv-${{ runner.os }}-${{ steps.pythonv.outputs.PYTHON_VERSION }}-${{ hashFiles('requirements.txt') }}
           path: .venv