Add "phpstan/extension-installer" to allowed plugins #220

Job	Run time
PHP 8.1, ubuntu-latest, prefer-lowest	21s
PHP 8.1, ubuntu-latest, prefer-stable	16s
PHP 8.1, macos-latest, prefer-lowest	1m 37s
PHP 8.1, macos-latest, prefer-stable	1m 11s
PHP 8.1, windows-latest, prefer-lowest	35s
PHP 8.1, windows-latest, prefer-stable	38s
PHP 8.2, ubuntu-latest, prefer-lowest	11s
PHP 8.2, ubuntu-latest, prefer-stable	14s
PHP 8.2, macos-latest, prefer-lowest	1m 12s
PHP 8.2, macos-latest, prefer-stable	1m 14s
PHP 8.2, windows-latest, prefer-lowest	40s
PHP 8.2, windows-latest, prefer-stable	42s
PHP 8.3, ubuntu-latest, prefer-lowest	19s
PHP 8.3, ubuntu-latest, prefer-stable	16s
PHP 8.3, macos-latest, prefer-lowest	1m 32s
PHP 8.3, macos-latest, prefer-stable	1m 7s
PHP 8.3, windows-latest, prefer-lowest	35s
PHP 8.3, windows-latest, prefer-stable	34s
PHP 8.4, ubuntu-latest, prefer-lowest	17s
PHP 8.4, ubuntu-latest, prefer-stable	13s
PHP 8.4, macos-latest, prefer-lowest	1m 16s
PHP 8.4, macos-latest, prefer-stable	1m 20s
PHP 8.4, windows-latest, prefer-lowest	35s
PHP 8.4, windows-latest, prefer-stable	34s
	17m 29s

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