cubicweb-tracker #3603300 migration shouldn't have renamed todo_by rtype [validation pending]

this rtype is used by other cubes. we just broke them.

priorityimportant
typebug
done in1.15.1
load1.000
load left0.000
closed by#ef50da6b1f24 [migration] Try to fix damage from 1.15.0
patch[migration] Try to fix damage from 1.15.0 [applied]