add note about what happens on button clicks

thx to @jospoortvliet for human understandable text

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

templates/Settings/personal.php

@@ -29,6 +29,7 @@ script('data_request', ['init', 'app']);
 
 <div id="data-request" class="section">
 	<h2><?php p($l->t('Account')); ?></h2>
+	<p><?php p($l->t('You can request an export of your data or account deletion from the system administrator. This can take up to 30 days to be executed.')); ?></p>
 	<div>
 		<button id="data-request-export" data-request="export" class="button"><?php p($l->t('Request data export')); ?></button><span class="warning hidden"></span>
 	</div>