[ticket/10734] Removed all the unnecessary corner classes

Removed the corner span classes from all the template and theme files.

PHPBB-10734

phpBB/styles/prosilver/template/mcp_notes_front.html

@@ -5,7 +5,7 @@
 <h2>{L_TITLE}</h2>
 
 <div class="panel">
-	<div class="inner"><span class="corners-top"><span></span></span>
+	<div class="inner">
 
 	<fieldset>
 	<dl>
@@ -15,7 +15,7 @@
 	</dl>
 	</fieldset>
 
-	<span class="corners-bottom"><span></span></span></div>
+	</div>
 </div>
 
 <fieldset class="submit-buttons">