members: Fix broken xref, change Diversity Advisor -> D&I Advisor
This commit fixes a broken xref to the "Biography" section on the role
page for the D&I Advisor. I used an `_` when I should have used a `-`.
I also changed the wording to "Diversity & Inclusion Advisor" from
"Diversity Advisor". This matches the wording used on the role page, and
the name preferred by the D&I Team.
Signed-off-by: Justin W. Flory (he/him) <git@jwf.io>