perf(mongodb): optimize event inbox query for better index utilization

Replace negation operator (!x.Processed) with equality comparison (x.Processed == false)
in MongoDbContextEventInbox.GetWaitingEventsAsync to improve MongoDB query performance.
This change converts the $ne operator to an equality match, allowing better index
utilization and more efficient queries, especially for large collections.

framework/src/Volo.Abp.MongoDB/Volo/Abp/MongoDB/DistributedEvents/MongoDbContextEventInbox.cs

@@ -64,7 +64,7 @@ public class MongoDbContextEventInbox<TMongoDbContext> : IMongoDbContextEventInb
         var outgoingEventRecords = await dbContext
             .IncomingEvents
             .AsQueryable()
-            .Where(x => !x.Processed)
+            .Where(x => x.Processed == false)
             .WhereIf(transformedFilter != null, transformedFilter!)
             .OrderBy(x => x.CreationTime)
             .Take(maxCount)