Dead flockdrones are not removed from the flockmind list

[DaedalusDock-Services]

Reporting client info:

BYOND:516.1663
Key:arturlang

Round ID:

312

Testmerges:

• The Flock of the Divine Monarch

Reproduction:

Dead flockdrones have maptext and appear in the flockmind list, they should also be possible to deconstruct too