Upgrade mkdocs so that jinja2 bug doesn't cause a problem. (#153)
Upgrade mkdocs so that jinja2 bug doesn't cause a problem. (#153)

See: https://github.com/mkdocs/mkdocs/issues/2799

* force older jinja until proto plugin is updated.

substrait-io/substrait,substrait-io/substrait,substrait-io/substrait,substrait-io/substrait