Updates from copilot feedback.

Author: ajcvickers

src/MongoDB.Driver/Core/Connections/CommandEventHelper.cs

@@ -223,7 +223,7 @@ public void ErrorReceiving(int responseTo, ConnectionId connectionId, ObjectId?
 
         public void ConnectionFailed(ConnectionId connectionId, ObjectId? serviceId, Exception exception, bool skipLogging)
         {
-            if (!_shouldTrackFailed && _tracingDisabled)
+            if (!_shouldTrackFailed && (_tracingDisabled || !MongoTelemetry.ActivitySource.HasListeners()))
             {
                 return;
             }

tests/SmokeTests/MongoDB.Driver.SmokeTests.Sdk/LibmongocryptTests.cs

@@ -59,8 +59,7 @@ public void Explicit_encryption_with_libmongocrypt_package_works()
                 kmsProviders.Add("local", localKey);
 
                 var keyVaultNamespace = CollectionNamespace.FromFullName("encryption.__keyVault");
-                var connectionString = Environment.GetEnvironmentVariable("MONGODB_URI");
-                var keyVaultMongoClient = string.IsNullOrWhiteSpace(connectionString) ? new MongoClient() : new MongoClient(connectionString);
+                var keyVaultMongoClient = new MongoClient(InfrastructureUtilities.MongoUri);
                 var clientEncryptionSettings = new ClientEncryptionOptions(
                     keyVaultMongoClient,
                     keyVaultNamespace,