Fix docs build error

Author: giswqs

.github/workflows/docs.yml

@@ -21,5 +21,5 @@ jobs:
             #   run: |
             #       python -m unittest discover tests/
             - run: python -m pip install --upgrade pip
-            - run: pip install mkdocs-material mkdocstrings mkdocstrings-python-legacy mkdocs-git-revision-date-plugin mkdocs-jupyter ipykernel
+            - run: pip install mkdocs-material mkdocstrings mkdocstrings-python mkdocs-git-revision-date-plugin mkdocs-jupyter ipykernel
             - run: mkdocs gh-deploy --force