Add "phpstan/extension-installer" to allowed plugins #211

Job	Run time
PHP 8.1, ubuntu-latest, prefer-lowest	25s
PHP 8.1, ubuntu-latest, prefer-stable	22s
PHP 8.1, macos-latest, prefer-lowest	1m 12s
PHP 8.1, macos-latest, prefer-stable	1m 12s
PHP 8.1, windows-latest, prefer-lowest	38s
PHP 8.1, windows-latest, prefer-stable	42s
PHP 8.2, ubuntu-latest, prefer-lowest	16s
PHP 8.2, ubuntu-latest, prefer-stable	13s
PHP 8.2, macos-latest, prefer-lowest	1m 14s
PHP 8.2, macos-latest, prefer-stable	1m 8s
PHP 8.2, windows-latest, prefer-lowest	45s
PHP 8.2, windows-latest, prefer-stable	39s
PHP 8.3, ubuntu-latest, prefer-lowest	18s
PHP 8.3, ubuntu-latest, prefer-stable	15s
PHP 8.3, macos-latest, prefer-lowest	1m 14s
PHP 8.3, macos-latest, prefer-stable	1m 18s
PHP 8.3, windows-latest, prefer-lowest	37s
PHP 8.3, windows-latest, prefer-stable	33s
PHP 8.4, ubuntu-latest, prefer-lowest	17s
PHP 8.4, ubuntu-latest, prefer-stable	10s
PHP 8.4, macos-latest, prefer-lowest	1m 23s
PHP 8.4, macos-latest, prefer-stable	1m 17s
PHP 8.4, windows-latest, prefer-lowest	35s
PHP 8.4, windows-latest, prefer-stable	33s
	17m 16s

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