In an effort to shorten our splash page, much of the previous
content has been added to our Infra Manual in the form of an FAQ.
Remove the sections which are now redundant, and link to the new
location.
With the removal of prior sections dropping some useful context, the
Free Software Needs Free Tools section is rephrased so that it
stands better on its own.
Also move the donors list to the very bottom of the page. This keeps
our content together, and still puts the list in a noticeable
location.
While we're here, drop the "What is OpenDev" section header since
it's superfluous.
Change-Id: I7a53907e9ef413f6c5db241fe59218f8db1d58bc
Depends-On: https://review.opendev.org/c/opendev/infra-manual/+/949924
a6f063e344