ci: docs use latest python

Author: resmo

.github/workflows/docs.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v6
         with:
-          python-version: "3.8"
+          python-version: "3.x"
 
       - name: Upgrade pip
         run: |
@@ -29,7 +29,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: ${{ steps.pip-cache.outputs.dir }}
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements-docs.txt') }}
           restore-keys: |
             ${{ runner.os }}-pip-