Remove implicit conversions

Since 2020, nlohmann has recognized that implicit conversions to and
from json are an issue.  Many bugs have been caused at both development
time and runtime due to unexpected implicit conversions from json to
std::string/int/bool.  This commit disables implicit conversions using
JSON_USE_IMPLICIT_CONVERSIONS [1].  This option will become the default
in the future.  That comment was written 3 years ago at this point, so
we should prepare.

Tested:
Redfish service validator passes.

[1] https://json.nlohmann.me/api/macros/json_use_implicit_conversions/
Change-Id: Id6cc47b9bbf8889e4777fd6d77ec992f3139962c
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/redfish-core/lib/task.hpp b/redfish-core/lib/task.hpp
index d0f2b07..4972c7d 100644
--- a/redfish-core/lib/task.hpp
+++ b/redfish-core/lib/task.hpp
@@ -244,7 +244,7 @@
         // "Killed" = taskRemoved
         // "Exception" = taskCompletedWarning
         // "Cancelled" = taskCancelled
-        nlohmann::json event;
+        nlohmann::json::object_t event;
         std::string indexStr = std::to_string(index);
         if (state == "Starting")
         {