Drop support for Symfony versions <5.4 #173

Job	Run time
PHPUnit (php-http/guzzle7-adapter php-http/discovery:^1.12, 7.3, lowest, weak, stable)	41s
PHPUnit (php-http/guzzle7-adapter php-http/vcr-plugin:^1.0@dev, 7.3, weak)	29s
PHPUnit (php-http/guzzle6-adapter, 7.4, weak)	22s
PHPUnit (php-http/guzzle7-adapter, 8.0, weak)	18s
PHPUnit (php-http/guzzle7-adapter, 8.1, weak)	28s
PHPUnit (php-http/guzzle7-adapter, 8.2, weak)	31s
PHPUnit (php-http/guzzle7-adapter php-http/curl-client:^2.0.0 php-http/vcr-plugin:^1.0@dev php-ht...	24s
PHPUnit (php-http/guzzle7-adapter php-http/vcr-plugin:^1.0@dev, 8.2, dev, weak)	24s
PHPUnit (php-http/guzzle7-adapter, 8.2, dev, weak)	34s
PHPUnit (php-http/guzzle7-adapter symfony/http-client:^5.4, 5.4.*, 7.3, weak)	33s
PHPUnit (php-http/guzzle7-adapter symfony/http-client:^6.0, 6.3.*, 8.2, weak)	22s
	5m 6s

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