How to remove message from task workflow form, \The content of this item will be sent as an e-mail message to the person or group assigned to the item\"

You can do it with Nintex Forms

have you tried using css?

I wanted to try CSS but this message doesn't appear to have any unique classes or ID's associated to it. 

Hi 

Can you confirm that it does not have an unique class?  The following script worked for me before.

NWF$(document).ready(function()
{

NWF$(".nf-infomessage").hide();

});

Thomas,

I finally did find the class of ms-informationbar so I replaced nf-infomessage with that in your script and that seems to have worked.  Thanks so much!

Teresa

Go to the workflow tasks list settings. Under advanced there is a section about emailing when task assignment changes. 

This worked !