allow not explicitly enabling savepoints with DBAL 4 #142

Job	Run time
Test (7.3, test_phpunit_legacy)	1m 7s
Test (7.4, --prefer-lowest, test_phpunit_legacy)	1m 3s
Test (7.4, 5.4.*, test_phpunit_legacy)	1m 26s
CS-Fixer	19s
php-stan	18s
Test (8, test_phpunit_legacy)	1m 22s
Test (8.1, test)	1m 37s
Test (8.2, 6.3.*, test)	1m 26s
Test (8.3, 6.4.*, test)	1m 2s
Test (8.2, 7.0.*, test)	1m 35s
Test (8.3, dev, test)	1m 39s
	12m 54s

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