Don't hardcode userinfo's min-height

While the value seems to be near what the 'involved' box may take, it's
usually wasting a lot of space (375px vs 520px in saschpe's case).

http://wstaw.org/m/2013/11/12/obshomecss.png
vs
http://wstaw.org/m/2013/11/12/obshomecss1.png