groups-js: add ourselves to admin in group-update reducer
groups-js: add ourselves to admin in group-update reducer

Fixes #3825

ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit