Mark nullable EntityRepository methods as impure #219

Job	Run time
Platform test (7.4)	3m 16s
Platform test (8.0)	3m 13s
Platform test (8.1)	2m 54s
Platform test (8.2)	3m 8s
Platform test (8.3)	3m 19s
Platform test (8.4)	2m 36s
Platform test (8.1, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 59s
Platform test (8.2, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 53s
Platform test (8.3, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 31s
Platform test (8.4, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 23s
	29m 12s

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