Update spring framework boot version to 2.6.6

pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
-    <version>2.6.4</version>
+    <version>2.6.6</version>
     <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>org.openepics</groupId>