misc: (temporary) - fix CI

For now, sphinx 6.0 is broken, so we can keep 5.3 until fixing doc
for 6.0

GitLab: #15
Change-Id: I2a708f5218f9566fafd96349c80268ecece5796e

_build/Dockerfile.build

@@ -19,4 +19,5 @@ USER jenkins
 
 ENV PATH="/home/jenkins/.local/bin:${PATH}"
 
-RUN pip3 install Sphinx sphinx-intl sphinx-rtd-theme myst-parser
+RUN pip3 install --upgrade sphinx==5.3.0
+RUN pip3 install sphinx-intl sphinx-rtd-theme myst-parser