CSHARP-2761: Fix error message in command monitoring test runner

Author: vincentkam

tests/MongoDB.Driver.Tests/Specifications/command-monitoring/TestRunner.cs

@@ -161,7 +161,7 @@ public void RunTestDefinition(IEnumerable<BsonDocument> data, string databaseNam
             var expectations = (BsonArray)definition["expectations"];
             if (!SpinWait.SpinUntil(() => __capturedEvents.Count == expectations.Count, TimeSpan.FromSeconds(5)))
             {
-                throw new Exception($"Expected {__capturedEvents.Count} events but only {expectations.Count} events were captured.");
+                throw new Exception($"Expected {expectations.Count} events but only {__capturedEvents.Count} events were captured.");
             }
 
             long? operationId = null;