Fix Allow ignoreMigrationPatterns to be empty

Removes the `.whenNot(List::isEmpty)` check to allow clearing the property.
The property's default is aligned with Flyway's to avoid breaking
existing behavior, and new tests verify both changes.

Signed-off-by: Chanwon-Seo <[email protected]>

Author: Chanwon-Seo

module/spring-boot-flyway/src/test/java/org/springframework/boot/flyway/autoconfigure/FlywayPropertiesTests.java

@@ -30,7 +30,6 @@
 import org.flywaydb.core.api.configuration.ClassicConfiguration;
 import org.flywaydb.core.api.configuration.Configuration;
 import org.flywaydb.core.api.configuration.FluentConfiguration;
-import org.flywaydb.core.api.pattern.ValidatePattern;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.BeanWrapper;