Update sharedbymail template

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

apps/sharebymail/templates/mail.php

@@ -27,9 +27,8 @@
 	<tr><td>
 			<table cellspacing="0" cellpadding="0" border="0" width="600px">
 				<tr>
-					<td bgcolor="<?php p($theme->getMailHeaderColor());?>" width="20px">&nbsp;</td>
-					<td bgcolor="<?php p($theme->getMailHeaderColor());?>">
-						<img src="<?php p(\OC::$server->getURLGenerator()->getAbsoluteURL(image_path('', 'logo-mail.gif'))); ?>" alt="<?php p($theme->getName()); ?>"/>
+					<td colspan="2" bgcolor="<?php p($theme->getMailHeaderColor());?>">
+						<img src="<?php p(\OC::$server->getURLGenerator()->getAbsoluteURL(image_path('', 'logo-mail.png'))); ?>" alt="<?php p($theme->getName()); ?>"/>
 					</td>
 				</tr>
 				<tr><td colspan="2">&nbsp;</td></tr>