Since the latest H2 version, the behavior of the drop table commands has changed to respect the SQL standard.
H2 used to ignore constraints when dropping table but now the drop fails.

The issue is that the current H2Dialect doesn't reflect this change yet: https://github.com/hibernate/hibernate-orm/blame/master/hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java#L438

A demo is also available here.
When the test is run, an error log is produced during the destroy phase:

2019-11-07 18:15:19.056 ERROR 18456 --- [extShutdownHook] .SchemaDropperImpl$DelayedDropActionImpl : HHH000478: Unsuccessful: drop table a if exists