fix(monitoring): correct spelling mistake for heartbeat event

Author: mbroadst

lib/core/sdam/monitoring.js

@@ -162,7 +162,7 @@ function monitorServer(server, options) {
 
         const isMaster = result.result;
         server.emit(
-          'serverHeartbeatSucceded',
+          'serverHeartbeatSucceeded',
           new ServerHeartbeatSucceededEvent(duration, isMaster, server.name)
         );