Update our releasers list

[hlandau]

Our releasers list seems out of date. Also, we now sign releases using the OMC key, so the releasers documentation in the repository seems out of date and in need of an update. Do we still need a releasers list? If so, do we need to add and remove any people from that list?

[nhorman]

Proposal: Replace the releaser list and only publish the team signing key

[nhorman]

also: update downloads page