Set springSecurityVersion to 5.4.+

Closes gh-119

gradle/dependency-management.gradle

@@ -3,7 +3,7 @@ if (!project.hasProperty("springVersion")) {
 }
 
 if (!project.hasProperty("springSecurityVersion")) {
-	ext.springSecurityVersion = "5.3.+"
+	ext.springSecurityVersion = "5.4.+"
 }
 
 if (!project.hasProperty("reactorVersion")) {