## Environment
**Liquibase Version**: 4.0.0

**Liquibase Integration & Version**: maven

**Database Vendor & Version**: postgresql 9 running in docker container from dockerHub

**Operating System Type & Version**: macOS Catalina 10.15.6

## Description
for createSequence with xml changeLog file Liquibase uses [AS] syntax when generating SQL. This is not supported by PostgreSQL prior to 10th version
https://docs.liquibase.com/change-types/community/create-sequence.html
https://www.postgresql.org/docs/9.6/sql-createsequence.html vs https://www.postgresql.org/docs/10/sql-createsequence.html

## Steps To Reproduce
clone https://github.com/liquibase/liquibase-test-harness
run ChangeObjectsTest from IDE as JUnit test or from cmd

`mvn failsafe:integration-test -DchangeObjects=createSequence -DinputFormat=xml`
 however input in sql format without `AS int` works
`mvn failsafe:integration-test -DchangeObjects=createSequence -DinputFormat=sql`

or just create xml changeLog with following
`<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
         http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.8.xsd">

```
<changeSet author="oleh" id="1">
    <createSequence dataType="int"
                    incrementBy="1"
                    minValue="1"
                    schemaName="public"
                    sequenceName="test_sequence"
                    startValue="1"/>
    <rollback>
        <dropSequence sequenceName="test_sequence"/>
    </rollback>
</changeSet>
```

</databaseChangeLog>`
and run it agains DB with enough access rights for creating sequences

## Actual Behavior
for postgreSQL <10 it is
`CREATE SEQUENCE  IF NOT EXISTS public.test_sequence AS int START WITH 1 INCREMENT BY 1 MINVALUE 1`

## Expected/Desired Behavior
`CREATE SEQUENCE  IF NOT EXISTS public.test_sequence START WITH 1 INCREMENT BY 1 MINVALUE 1`


}
            }
        }
        if (!(database instanceof MariaDBDatabase) && statement.getOrdered() != null) {
            if (!(database instanceof SybaseASADatabase)) {
                if (statement.getOrdered()) {
                    queryStringBuilder.append(" ORDER");
                } else {
                   if (database instanceof OracleDatabase) {
                       queryStringBuilder.append(" NOORDER");
                   }
                }
            }
        }
        if (!(database instanceof MariaDBDatabase) && statement.getCycle() != null) {
            if (statement.getCycle()) {
                queryStringBuilder.append(" CYCLE");
            }
        }
        return new Sql[]{new UnparsedSql(queryStringBuilder.toString(), getAffectedSequence(statement))};
    }
    protected Sequence getAffectedSequence(CreateSequenceStatement statement) {
        return new Sequence().setName(statement.getSequenceName()).setSchema(statement.getCatalogName(), statement.getSchemaName());
    }
    private boolean isH2WithMinMaxSupport(Database database) {
        return H2Database.class.isAssignableFrom(database.getClass())
                && ((H2Database) database).supportsMinMaxForSequences();
    }
}