Remove 'send a message' button for retired Lords

[MyfanwyNixon]

See also #1406

A user mentions that they tried to contact https://www.theyworkforyou.com/peer/13565/lord_macdonald_of_tradeston#profile and was told that he'd resigned in 2017. See https://www.parliament.uk/mps-lords-and-offices/lords/retired-lords/