[DRE-maint] ruby-devise-async is marked for autoremoval from testing

[Debian testing autoremoval watch]

ruby-devise-async 0.9.0-1 is marked for autoremoval from testing on 2016-10-27

It is affected by these RC bugs:
837638: ruby-devise-async: Incompatible with ruby-devise 4
837644: ruby-devise-async: ruby-devise-async is not compatible with devise >= 4.0