Fix pipeline documentation build

The ci/cd pipeline is divided into two stages (build and deploy). The build stage is executed in every branch. Deployment is only executed for the master branch. This enables testing of the pipeline.

Fixing the sphinx version to 5.0.2 and removing dependencies to the additional sphinx packages, fixes the crash of the doc building jobs.

.gitlab-ci.yml

 image: python:3.7
 
 stages:
-    - build_wheel
-    - build_doc
+    - build
+    - deploy
  
-wheel:
+before_script:
+    - pip install --upgrade pip
+
+build_wheel:
+    tags:
+        - wheel
+    stage: build
+    script:
+        - pip install --upgrade setuptools wheel
+        - python setup.py bdist_wheel
+
+build_docs:
+    tags:
+        - doc
+    stage: build
+    script:
+       - pip install -r requirements.txt
+       - cd docs
+       - make html
+
+deploy_wheel:
     tags:
         - wheel
-    stage: build_wheel
+    stage: deploy
     script:
-        - pip install --upgrade pip setuptools wheel
+        - pip install --upgrade setuptools wheel
         - python setup.py bdist_wheel
         - mv dist/ public
     
@@ -20,12 +40,12 @@ wheel:
     only:
         - master
 
-pages:
+deploy_pages:
     tags:
         - doc
-    stage: build_doc
+    stage: deploy
     dependencies:
-       - wheel
+       - deploy_wheel
     script:
        - pip install -r requirements.txt
        - cd docs
@@ -36,4 +56,4 @@ pages:
         paths:
            - public
     only:
-       - master
+       - master
\ No newline at end of file