build(deps): bump actions/cache from 3 to 4

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]>

Author: dependabot[bot]

.github/workflows/ci_docs.yml

@@ -35,7 +35,7 @@ jobs:
           python-version: 3.8
 
       - name: Cache pip
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/.cache/pip
           key: pip-${{ hashFiles('requirements.txt') }}-${{ hashFiles('_requirements/docs.txt') }}

.github/workflows/ci_test-acts.yml

@@ -38,7 +38,7 @@ jobs:
         run: echo "::set-output name=dir::$(pip cache dir)"
 
       - name: pip cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ${{ steps.pip-cache.outputs.dir }}
           key: ${{ runner.os }}-pip-py${{ matrix.python-version }}-${{ hashFiles('.actions/requires.txt') }}-${{ hashFiles('requirements/default.txt') }}

.github/workflows/docs-deploy.yml

@@ -24,7 +24,7 @@ jobs:
           python-version: 3.8
 
       - name: Cache pip
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}-${{ hashFiles('_requirements/docs.txt') }}