amended mkdocs missing message to allign with sphinx#12012

silentfatez wants to merge 3 commits intoreadthedocs:mainreadthedocs/readthedocs.org:mainfrom

silentfatez:mkdocs-build-missing-yaml-messagesilentfatez/readthedocs.org:mkdocs-build-missing-yaml-messageCopy head branch name to clipboard