entity_manager: Remove unused local variable

The local object variable 'systemConfiguration' in main() function is
not used, it is changed to public member value of 'class EntityManager'
by the commit cf6a75bd2bbf ("Introduce EntityManager class").

Change-Id: I28fe6814c2b7c1aecd4aa54583304ba7e6179711
Signed-off-by: Haiyue Wang <haiyuewa@163.com>
diff --git a/src/entity_manager/main.cpp b/src/entity_manager/main.cpp
index 3a80366..ebd27f8 100644
--- a/src/entity_manager/main.cpp
+++ b/src/entity_manager/main.cpp
@@ -15,8 +15,6 @@
     systemBus->request_name("xyz.openbmc_project.EntityManager");
     EntityManager em(systemBus, io);
 
-    nlohmann::json systemConfiguration = nlohmann::json::object();
-
     boost::asio::post(io, [&]() { em.propertiesChangedCallback(); });
 
     em.handleCurrentConfigurationJson();