BAEL-20663: Temporarly downgrade Spring Boot to 2.1.9 in spring-boot-admin

spring-boot-admin/pom.xml

@@ -11,6 +11,7 @@
         <groupId>com.baeldung</groupId>
         <artifactId>parent-boot-2</artifactId>
         <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-boot-2</relativePath>
     </parent>
 
     <modules>
@@ -18,4 +19,8 @@
         <module>spring-boot-admin-client</module>
     </modules>
 
+    <properties>
+        <spring-boot.version>2.1.9.RELEASE</spring-boot.version>
+    </properties>
+
 </project>