CI documentation step does not ship

As I understand, the docs compilation is done by readthedocs locally, it pulls changes each time the webhook is triggered, for branch or tags flagged as "active" in reathedocs.
So the shipping step in the CI is not required, except for us when we want to test the compilation after changes to the code, in order to catch errors before readthedocs does.
Thus I think we can keep the CI job, but only on docs changes (md or yaml), since it's not useful to compile it only when tags are pushed.

But we still need the test before it's merged in develop, and compiled for the url https://pyotb.readthedocs.io/en/develop/