Fix clang-tidy issue in aggregation

clang-tidy flags the following error, which is correct.

```
../redfish-core/include/query.hpp:145:26: error: static member accessed through instance [readability-static-accessed-through-instance,-warnings-as-errors]
    needToCallHandlers = RedfishAggregator::getInstance().beginAggregation(
```

Tested (Carson):
Verified that queries to top level collections as well as aggregated
resources still return as expected.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I440fb29d2e0b3da52bfd564676d33b72f69f2fbc
Signed-off-by: Carson Labrado <clabrado@google.com>
diff --git a/redfish-core/include/query.hpp b/redfish-core/include/query.hpp
index 1fb0bd8..10a337b 100644
--- a/redfish-core/include/query.hpp
+++ b/redfish-core/include/query.hpp
@@ -148,8 +148,8 @@
     bool needToCallHandlers = true;
 
 #ifdef BMCWEB_ENABLE_REDFISH_AGGREGATION
-    needToCallHandlers = RedfishAggregator::getInstance().beginAggregation(
-                             req, asyncResp) == Result::LocalHandle;
+    needToCallHandlers = RedfishAggregator::beginAggregation(req, asyncResp) ==
+                         Result::LocalHandle;
 
     // If the request should be forwarded to a satellite BMC then we don't want
     // to write anything to the asyncResp since it will get overwritten later.