Remove the custom stub file which is now part of phpstan/phpstan-nette #2525

Job	Run time
check-file-patterns	5s
composer-validate (8.4)	5s
info (8.4)	9s
check-makefile (8.4)	9s
check-sri-macros-concat	5s
composer-dependency-analyser (8.4)	10s
lint-latte (8.4)	9s
lint-neon (8.4)	9s
lint-php (8.4)	12s
lint-xml	13s
phpcs (8.4)	13s
phpstan (8.4)	27s
phpstan-vendor (8.4)	1m 9s
psalm (8.3)	18s
tester (8.4)	16s
	3m 49s

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