CI: Enable pip caching

Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

Diff for: .github/workflows/ci.yaml

@@ -17,6 +17,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.13"
+          cache: 'pip'
       - name: Set up Go
         uses: actions/setup-go@v5
         with:
@@ -76,6 +77,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python }}
+          cache: 'pip'
       - name: Install Python dependencies
         run: python -m pip install tox tox-gh-actions
       - name: Log database configuration (mysql)
@@ -109,6 +111,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.13"
+          cache: 'pip'
       - name: Install dependencies
         run: python -m pip install tox
       - name: Build docs (via tox)
@@ -136,6 +139,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.13"
+          cache: 'pip'
       - name: Build docker-compose service
         run: |
           docker compose build --build-arg UID=$(id -u) --build-arg GID=$(id -g)