Bump phpstan/phpstan from 1.12.7 to 2.0.0 #311

Job	Run time
Dynamic version matrix	3s
Docker [2.2.2] + Nginx (no websocket)	25s
Docker [2.0.2] + Nginx (no websocket)	37s
Docker [1.8.17] + Nginx (no websocket)	48s
Docker [2.0.0] + Nginx (no websocket)	31s
Docker [1.9.7] + Nginx (without subpath)	46s
Source [develop] with plugins	40s
Docker [latest]	29s
Docker [develop] + Nginx (with subpath)	29s
Docker [2.2.6] + Nginx (with subpath)	39s
Docker [2.1.0] + Nginx (with subpath)	26s
Docker [2.0.2] + Nginx (with subpath)	37s
Docker [2.0.0] + Nginx (with subpath)	36s
Docker [develop]	29s
Docker [2.2.6]	31s
Docker [1.9.7] + Nginx (with subpath)	44s
Docker [1.8.18] + Nginx (with subpath)	45s
Docker [2.1.0]	30s
Docker [1.8.0] + Nginx (with subpath)	29s
Docker [2.0.2]	33s
Docker [2.0.0]	29s
Docker [1.7.5] + Nginx (with subpath)	34s
Docker [1.9.7]	55s
Docker [1.8.18]	56s
Docker [1.8.0]	18s
Docker [1.7.5]	36s
	14m 55s

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