chore: update Spring Boot version to 2.3.4

Author: BlasiusSecundus

gradle.properties

@@ -40,7 +40,7 @@ TARGET_COMPATIBILITY = 1.8
 ### Dependencies
 
 LIB_GRAPHQL_JAVA_VER = 14.1
-LIB_SPRING_BOOT_VER = 2.3.1.RELEASE
+LIB_SPRING_BOOT_VER = 2.3.4.RELEASE
 LIB_GRAPHQL_SERVLET_VER = 9.2.0
 LIB_GRAPHQL_JAVA_TOOLS_VER = 6.1.0
 LIB_GRAPHQL_ANNOTATIONS_VER = 8.1