[fenix] Update the description for an inactive tabs string

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

@@ -1791,7 +1791,7 @@
     <!-- In-activate tabs in the tabs tray -->
     <!-- Title text displayed in the tabs tray when a tab has been unused for 4 days. -->
     <string name="inactive_tabs_title">Inactive tabs</string>
-    <!-- A description below the section of "inactive" tabs to notify the user when those tabs will be closed, if appropriate. -->
+    <!-- A description below the section of "inactive" tabs to notify the user when those tabs will be closed, if appropriate. See strings inactive_tabs_30_days and inactive_tabs_7_days for placeholders options. -->
     <string name="inactive_tabs_description">Tabs are available here for %s. After that time, tabs will be automatically closed.</string>
     <!-- The amount of time until a tab in the "inactive" section of the tabs tray will be closed. See string inactive_tabs_description as well -->
     <string name="inactive_tabs_30_days">30 days</string>