fix tests

Author: sanych-sun

tests/MongoDB.Driver.Tests/Core/Operations/AsyncCursorTests.cs

@@ -693,7 +693,7 @@ private void AssertExpectedSessionReferenceCount(ICoreSessionHandle session, IAs
         {
             var cursorImplementation = (AsyncCursor<BsonDocument>)cursor;
             var cursorId = cursorImplementation._cursorId();
-            var expectedReferenceCount = cursorId == 0 ? 2 : 3; // one from the session, and one from the cursor
+            var expectedReferenceCount = cursorId == 0 ? 1 : 2; // one from the session, and one from the cursor
             session.ReferenceCount().Should().Be(expectedReferenceCount);
         }