HHH-13711: drop constraints enabled for H2

hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java

@@ -435,10 +435,8 @@ public class H2Dialect extends Dialect {
 	}
 	
 	@Override
-	public boolean dropConstraints() {
-		// We don't need to drop constraints before dropping tables, that just leads to error
-		// messages about missing tables when we don't have a schema in the database
-		return false;
+	public boolean supportsIfExistsAfterAlterTable() {
+		return true;
 	}
 
 	@Override