Fixed issue with notification dropdownn not updating active

Changes bell icon to spinner to show the action is happening
Removed the flash message

Closes #18480

app/assets/javascripts/notifications_dropdown.js.coffee

 class @NotificationsDropdown
-  $ ->
+  constructor: ->
     $(document)
       .off 'click', '.update-notification'
       .on 'click', '.update-notification', (e) ->
@@ -18,7 +18,8 @@ class @NotificationsDropdown
       .off 'ajax:success', '.notification-form'
       .on 'ajax:success', '.notification-form', (e, data) ->
         if data.saved
-          new Flash('Notification settings saved', 'notice')
-          $(e.currentTarget).closest('.notification-dropdown').replaceWith(data.html)
+          $(e.currentTarget)
+            .closest('.notification-dropdown')
+            .replaceWith(data.html)
         else
           new Flash('Failed to save new settings', 'alert')

app/assets/javascripts/project.js.coffee

@@ -35,7 +35,6 @@ class @Project
       $(@).parents('.no-password-message').remove()
       e.preventDefault()
 
-
     @projectSelectDropdown()
 
   projectSelectDropdown: ->

app/assets/stylesheets/pages/projects.scss

@@ -101,7 +101,8 @@
 
   .notifications-btn {
 
-    .fa-bell {
+    .fa-bell,
+    .fa-spinner {
       margin-right: 6px;
     }