fix pipeline building by updating the mkdocs versions
@grigoras currently pipeline is broken with error:
File "/usr/local/lib/python3.8/site-packages/mkdocs/utils/filters.py", line 13, in <module>
@jinja2.contextfilter
AttributeError: module 'jinja2' has no attribute 'contextfilter'
solution found: https://github.com/readthedocs/readthedocs.org/issues/9064