Cheng Luo

Update newest recurrentmaskable PPO on https://github.com/wdlctc/recurrent_maskable based on sb3-contrib version 1.8.0 since the previous version can't work on current version of sb3-contrib. Feel free to take it.

> > Update newest recurrentmaskable PPO on https://github.com/wdlctc/recurrent_maskable based on sb3-contrib version 1.8.0 > > Thanks for the update, do you mean it now works with current SB3 master version?...