[11.x] Add missing test for `implode()` #44892

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Job	Run time
PHP 8.2 - PHPUnit 10.5.35 - prefer-lowest	1m 53s
PHP 8.2 - PHPUnit 10.5 - prefer-lowest - Windows	2m 20s
PHP 8.2 - PHPUnit 10.5 - prefer-stable - Windows	2m 26s
PHP 8.2 - PHPUnit 10.5.35 - prefer-stable	1m 50s
PHP 8.2 - PHPUnit 11.0.1 - prefer-lowest - Windows	2m 16s
PHP 8.2 - PHPUnit 11.0.1 - prefer-stable - Windows	2m 17s
PHP 8.3 - PHPUnit 10.5 - prefer-lowest - Windows	2m 16s
PHP 8.2 - PHPUnit 11.3.2 - prefer-lowest	2m 1s
PHP 8.2 - PHPUnit 11.3.2 - prefer-stable	2m 0s
PHP 8.3 - PHPUnit 10.5 - prefer-stable - Windows	2m 16s
PHP 8.3 - PHPUnit 10.5.35 - prefer-lowest	2m 1s
PHP 8.3 - PHPUnit 11.0.1 - prefer-lowest - Windows	2m 18s
PHP 8.3 - PHPUnit 10.5.35 - prefer-stable	1m 58s
PHP 8.3 - PHPUnit 11.0.1 - prefer-stable - Windows	2m 19s
PHP 8.3 - PHPUnit 11.3.2 - prefer-lowest	1m 55s
PHP 8.4 - PHPUnit 10.5 - prefer-stable - Windows	2m 22s
PHP 8.3 - PHPUnit 11.3.2 - prefer-stable	1m 46s
PHP 8.4 - PHPUnit 11.0.1 - prefer-stable - Windows	2m 24s
PHP 8.3 - PHPUnit 12.0.0 - prefer-lowest	1m 58s
PHP 8.3 - PHPUnit 12.0.0 - prefer-stable	1m 43s
PHP 8.4 - PHPUnit 10.5.35 - prefer-lowest	1m 49s
PHP 8.4 - PHPUnit 10.5.35 - prefer-stable	1m 51s
PHP 8.4 - PHPUnit 11.3.2 - prefer-lowest	2m 3s
PHP 8.4 - PHPUnit 11.3.2 - prefer-stable	1m 49s
PHP 8.4 - PHPUnit 12.0.0 - prefer-lowest	1m 48s
PHP 8.4 - PHPUnit 12.0.0 - prefer-stable	1m 50s
	53m 29s

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