Fix "br" typo causing ugly rendering (epub only)
Fix "br" typo causing ugly rendering (epub only)

</br> instead of <br/> renders fine in the browser but not in an epub
butterflyology/rr-intro,Reproducible-Science-Curriculum/rr-literate-programming,dleehr/organization-RR-Jupyter,butterflyology/rr-intro,Reproducible-Science-Curriculum/rr-literate-programming,butterflyology/rr-intro,Reproducible-Science-Curriculum/rr-automation,dleehr/organization-RR-Jupyter,Reproducible-Science-Curriculum/rr-automation,dleehr/organization-RR-Jupyter,dleehr/organization-RR-Jupyter,butterflyology/rr-intro,dleehr/organization-RR-Jupyter,butterflyology/rr-intro,butterflyology/rr-intro,dleehr/organization-RR-Jupyter