Remove the [traceId, startTime] index on TaskEvent for now (not necessary)

Author: ericallam

packages/database/prisma/migrations/20240625091632_add_trace_id_start_time_index_on_task_events/migration.sql

@@ -1925,8 +1925,6 @@ model TaskEvent {
   @@index([traceId])
   /// Used when looking up span events to complete when a run completes
   @@index([spanId])
-  /// Used on eventRepository.getTraceSummary()
-  @@index([traceId, startTime])
   // Used for getting all logs for a run
   @@index([runId])
 }