Update file .gitlab-ci.yml

.gitlab-ci.yml

 # This file is a template, and might need editing before it works on your project.
 # Full project: https://gitlab.com/pages/plain-html
 
-image: python:3.8-alpine
+image: python:3.8-slim
 
 stages:
   - build
 
 pages:
-  tags:
-    - sphinx
-  stage: build
   script:
-    - python3 -m pip install sphinx rtd
+    - pip3 install -r requirements.txt
     - sphinx-build -b html docs/source/ public/
   artifacts:
     paths: