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](actions/cache@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>

Author: dependabot[bot]

.github/workflows/build-docs.yml

@@ -29,7 +29,7 @@ jobs:
         run: poetry config virtualenvs.in-project true
 
       - name: Set up cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         id: cache
         with:
           path: .venv

.github/workflows/python-test.yml

@@ -37,7 +37,7 @@ jobs:
         run: poetry config virtualenvs.in-project true
 
       - name: Set up cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         id: cache
         with:
           path: .venv
@@ -87,7 +87,7 @@ jobs:
         run: poetry config virtualenvs.in-project true
 
       - name: Set up cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         id: cache
         with:
           path: .venv