[TASK] Allow `assertInstanceOf` calls in tests #1579

Job	Run time
PHP Lint (7.2)	18s
PHP Lint (7.3)	11s
PHP Lint (7.4)	11s
PHP Lint (8.0)	12s
PHP Lint (8.1)	22s
PHP Lint (8.2)	12s
PHP Lint (8.3)	39s
PHP Lint (8.4)	11s
Static Analysis (composer:normalize, 8.3)	18s
Unit tests (7.2)	11s
Static Analysis (php:fixer, 8.3)	20s
Static Analysis (php:stan, 8.3)	31s
Unit tests (7.3)	24s
Static Analysis (php:rector, 8.3)	23s
Unit tests (7.4)	13s
Unit tests (8.0)	14s
Unit tests (8.1)	17s
Unit tests (8.2)	12s
Unit tests (8.3)	11s
Unit tests (8.4)	17s
	5m 47s

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