dbtest: remove statement_timeout
Created by: LawnGnome
#22756 added statement_timeout
to the DSN we use when connecting to test databases, which has then caused our CI to often fail because we have many tests that can take more than 30 seconds when cloning new test databases when our test environment is under load.
This PR removes that parameter.
Note that CI is currently failing on this PR due to the unrelated issue fixed by #22806.