[totem/mallard-documentation] Don't abuse <code> for non-code text

[Andre Klapper <aklapper src gnome org>]

commit 1c0579034f1a77eed3e3a5ae220d09a295c9805d
Author: Andre Klapper <a9016009 gmx de>
Date:   Fri Jan 11 23:08:21 2019 +0100

    Don't abuse <code> for non-code text

 help/C/supported-formats.page | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/help/C/supported-formats.page b/help/C/supported-formats.page
index ece57aba..a11d4baf 100644
--- a/help/C/supported-formats.page
+++ b/help/C/supported-formats.page
@@ -20,7 +20,7 @@
 
   <title>Cannot play a certain file format</title>
 
-  <p>File formats displayed by <app>Videos</app> depend on <gui>GStreamer</gui>
+  <p>File formats displayed by <app>Videos</app> depend on <sys>GStreamer</sys>
   plugins. If certain file formats are not supported, please refer to a support
   forum of your distribution to find out which package to install.</p>