Remove Psalm from the project #1309
Description
Since I started this project, psalm hasn't helped me even once to avoid any problematic bugs, I'm considering removing it entirely and focusing on phpstan which in my personal opinion is just more mature.
It's not a final decision yet so if anyone has any opinions about it, please share it here!
You are also welcome to share you thoughts even if you never contributed to Flow but has some past experience with phpstan/psalm
