Pin Sphinx to 2.4.4 to fix publishing

There seems to be an issue where the confluencepublisher
publishes garbage in the latest version of Sphinx. Pinning it
to a known working version and following up to fix the
regressing in the confluence publisher.

This should be temporary (famour last words).

Author: pratikmallya

Dockerfile

@@ -3,6 +3,7 @@ FROM python:3.5
 USER root
 
 RUN pip install \
+  Sphinx==2.4.4 \
   sphinxcontrib-confluencebuilder \
   recommonmark