One last fix for the slack inviter

Author: knolleary

slack/index.html

@@ -66,8 +66,7 @@ <h2 style="margin-top: 30px">Already a member? <a href="https://node-red.slack.c
         $.ajax({
             type: "POST",
             url: 'https://gnh34zyze1.execute-api.eu-west-2.amazonaws.com/default/nodeREDSlackInviter',
-            data: JSON.stringify({email:$('#e').val()}),
-            contentType : 'application/json',
+            data: {email:$('#e').val()},
             success: function(data,status) {
                 $('#go').attr('disabled',false);
                 if (!data.ok) {