Thanks for all your hard work, Zoxc! <3

Move Zoxc to alumni membership in the compiler team.

Also, adjust wg-parallel-rustc to more accurately reflect folks who've
been active recently. I'm putting down simulacrum as the lead (and
myself as the co-lead or liaison) since he was playing that
role. Regardless, we need to have a sync meeting to decide whether
this effort will continue and who will lead it up.