Fix PostgresAdapter not returning limit for char and varchar #989

Job	Run time
Windows - PHP 7.3 & SQL Server	3m 14s
Coding Standard & Static Analysis	37s
testsuite (7.3, sqlite)	31s
testsuite (7.3, mysql)	44s
testsuite (7.3, pgsql)	57s
testsuite (7.4, sqlite)	30s
testsuite (7.4, mysql)	50s
testsuite (7.4, pgsql)	59s
testsuite (8.0, sqlite)	21s
testsuite (8.0, mysql)	50s
testsuite (8.0, pgsql)	54s
testsuite (8.2, sqlite)	34s
testsuite (8.2, mysql)	52s
testsuite (8.2, pgsql)	55s
testsuite (7.3, mysql, prefer-lowest)	55s
	13m 43s

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