Revert "count both spans and traces"

This reverts commit d49bd89061.

src/agents/tracing/processors.py

@@ -81,17 +81,7 @@ class BackendSpanExporter(TracingExporter):
         traces: list[dict[str, Any]] = []
         spans: list[dict[str, Any]] = []
 
-        # Categorize items into traces and spans
+        data = [item.export() for item in items if item.export()]
-        for item in items:
-            if hasattr(item, 'export') and callable(item.export):
-                export_data = item.export()
-                if export_data:
-                    if isinstance(item, Trace):
-                        traces.append(export_data)
-                    else:
-                        spans.append(export_data)
-
-        data = traces + spans
         payload = {"data": data}
 
         headers = {