Remove test starter from core module

Closes gh-15463

Author: snicoll

spring-boot-project/spring-boot-properties-migrator/pom.xml

@@ -27,7 +27,7 @@
 		<!-- Test -->
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-test</artifactId>
+			<artifactId>spring-boot-test</artifactId>
 			<scope>test</scope>
 		</dependency>
 	</dependencies>