This commit completely drops all of the content in /engineering/ and
/mindshare/ modules, because we are publishing them twice:

https://gitlab.com/fedora/docs/docs-website/pages

This repository is where the docs.fp.o/engineering/ and
docs.fp.o/mindshare/ pages are actually getting generated from. The
source content in this repository appears to be duplicative. In the
interest of greater simplicity, we should remove things which are no
longer being used.

@pbokoc can verify whether the removal of this content will cause any
issues or breakages in the Fedora Docs publishing pipeline.