[fenix] Update tabs tray title header string comment to clarify what it does.

app/src/main/res/values/strings.xml

@@ -740,7 +740,7 @@
     <string name="pwa_site_controls_title_private">%1$s (Private Mode)</string>
     <!-- Button in the current tab tray header in multiselect mode. Saved the selected tabs to a collection when pressed. -->
     <string name="tab_tray_save_to_collection">Save</string>
-    <!-- Text for normal tabs header title. -->
+    <!-- Title text for the normal tabs header in the tabs tray which are not part of any tab grouping. -->
     <string name="tab_tray_header_title">Other</string>
 
     <!-- History -->