fix: Use pre-built dockerfile

.woodpecker.yml

@@ -1,17 +1,6 @@
 ---
 
 steps:
-  create_docker_image:
-    image: woodpeckerci/plugin-docker-buildx
-    settings:
-      repo: moanos/sphinx-rtd
-      dockerfile: docs/Dockerfile
-      tag: latest
-      username:
-        from_secret: docker_username
-      password:
-        from_secret: docker_password
-
   build:
     image: moanos/sphinx-rtd
     commands:

docs/Dockerfile

@@ -1,5 +0,0 @@
-FROM sphinxdoc/sphinx
-
-WORKDIR /docs
-COPY ./docs/requirements.txt /docs
-RUN pip3 install -r requirements.txt