Use older version of spring-boot-loader

Avoids class def not found issue owning to a change in the
behaviour of JarFileArchive in Spring Boot 2.2.

spring-cloud-launcher/spring-cloud-launcher-deployer/pom.xml

@@ -61,6 +61,11 @@
 	</dependencyManagement>
 
 	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-loader</artifactId>
+			<version>2.1.9.RELEASE</version>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.cloud</groupId>
 			<artifactId>spring-cloud-deployer-thin</artifactId>