Update copy for private mode (mozilla#12166)

Original statement was too broad as some data can still be collected by websites in private mode

bedrock/firefox/templates/firefox/family/includes/modules/private-mode.html

@@ -24,7 +24,7 @@
           </defs>
         </svg>
         <h3 class="c-subtitle">The private browsing mode paradox</h3>
-        <p>On the one hand it keeps your kid’s data from being collected
+        <p>On the one hand, private browsing can make it harder for advertisers to track your kid
           <em>*dramatic pause*</em> but it also erases their browsing history.</p>
       {% endcall %}