Remove unused variable

This hasn't been used in a while.  Remove it.

Tested: Code compiles.

Change-Id: I3134cee6e013a630cc7d17727c2f29de3a40fbc1
Signed-off-by: Ed Tanous <etanous@nvidia.com>
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/redfish-core/include/event_service_manager.hpp b/redfish-core/include/event_service_manager.hpp
index 4c2d0ee..9ab578d 100644
--- a/redfish-core/include/event_service_manager.hpp
+++ b/redfish-core/include/event_service_manager.hpp
@@ -47,9 +47,6 @@
 namespace redfish
 {
 
-using ReadingsObjType =
-    std::vector<std::tuple<std::string, std::string, double, int32_t>>;
-
 static constexpr const char* eventFormatType = "Event";
 static constexpr const char* metricReportFormatType = "MetricReport";