help: Update notification.page

Replace obsolete screenshots with new ones.
Fix alignment of mallard tags.
Update instructions for --listen.

help/C/notification.page

@@ -6,12 +6,9 @@
     <desc>Use the <cmd>--notification</cmd> option.</desc>
   </info>
   <title>Notification Icon</title>
-    <p>
-	Use the <cmd>--notification</cmd> option to create a notification icon.
-    </p>
+    <p>Use the <cmd>--notification</cmd> option to create a notification icon.</p>
 
   <terms>
-
     <item>
       <title><cmd>--text</cmd>=<var>text</var></title>
       <p>Specifies the text that is displayed in the notification area.</p>
@@ -25,16 +22,14 @@
     </item>
   </terms>
 
-    <p>
-      The following example script shows how to create a notification icon:
-    </p>
-<code>
-#!/bin/sh
+  <p>The following example script shows how to create a notification icon:</p>
+  <code>
+  #!/bin/sh
 
-zenity --notification\
+  zenity --notification\
     --window-icon="info" \
     --text="There are system updates necessary!"
-</code>
+  </code>
 
   <figure id="zenity-notification-screenshot">
     <title>Notification Icon Example</title>
@@ -42,17 +37,13 @@ zenity --notification\
     <media type="image" mime="image/png" src="figures/zenity-notification-screenshot.png"/>
   </figure>
 
-    <p>
-      The following example script shows how to create a notification icon along with <cmd>--listen</cmd>:
-    </p>
-
-<code>
-#!/bin/sh
-
-cat &#60;&#60;EOH| zenity --notification --listen
-message: this is the message text
-EOH
-</code>
+  <p>The following example script shows how to create a notification icon along with <cmd>--listen</cmd>:</p>
+  <code>
+  #!/bin/sh
+  cat &#60;&#60;EOH| zenity --notification --listen
+  message: this is the message text
+  EOH
+  </code>
 
   <figure id="zenity-notification-listen-screenshot">
     <title>Notification Icon with <cmd>--listen</cmd> Example</title>