Polish LiquibaseAutoConfigurationTests

[wilkinsona]

There's an accidental reference to FlywayAutoConfiguration that should not be there:

spring-boot/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/liquibase/LiquibaseAutoConfigurationTests.java

Line 878 in 6567609

<class>org.springframework.boot.autoconfigure.flyway.FlywayAutoConfigurationTests$City</class>