feat: Disable mozilla sponsors, b=no-bug, c=no-component

src/browser/themes/shared/preferences/zen-preferences.css

@@ -582,7 +582,9 @@ groupbox h2 {
 #dataCollectionGroup,
 #websiteAdvertisingCategory,
 #websiteAdvertisingGroup,
-#helpButton {
+#helpButton,
+#support-firefox,
+.mission-message {
   display: none !important;
 }
 
@@ -596,3 +598,9 @@ groupbox h2 {
     display: none;
   }
 }
+
+@media -moz-pref('zen.urlbar.replace-newtab') {
+  #category-home {
+    display: none !important;
+  }
+}