DOC: coobook fix math rendering
DOC: coobook fix math rendering

Don't overwrite math role:
https://github.com/sphinx-doc/sphinx/issues/2927#event-773707455

orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB,orfeotoolbox/OTB