fix(aggregation): fix field name typo

Author: Sintendo

lib/aggregation_cursor.js

@@ -148,7 +148,7 @@ AggregationCursor.prototype.batchSize = function(value) {
   if (this.s.state === AggregationCursor.CLOSED || this.isDead())
     throw MongoError.create({ message: 'Cursor is closed', driver: true });
   if (typeof value !== 'number')
-    throw MongoError.create({ message: 'batchSize requires an integer', drvier: true });
+    throw MongoError.create({ message: 'batchSize requires an integer', driver: true });
   if (this.s.cmd.cursor) this.s.cmd.cursor.batchSize = value;
   this.setCursorBatchSize(value);
   return this;