Change description of oldest reviews
Change description of oldest reviews

Make it more clear that the list of oldest reviews is just that, and not call it
a variant of calculating the longest waiting reviews.

Change-Id: I890f07519ceccfc57a5a73293817105a3b8c9f53

cp16net/reviewstats,JohnGarbutt/reviewstats,JohnGarbutt/reviewstats,openstack-infra/reviewstats,cp16net/reviewstats,openstack-infra/reviewstats