[Activiti-3093] Update Spring Boot to version 2.1.6.RELEASE (#176)

Ref Activiti/Activiti#2616

Author: erdemedeiros

pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
-    <version>2.1.2.RELEASE</version>
+    <version>2.1.6.RELEASE</version>
     <relativePath /> <!-- lookup parent from repository -->
   </parent>
   <groupId>org.activiti.cloud.examples</groupId>