docs: fix html end/start tags

for more well-formed html

Signed-off-by: Brian Paul <brianp@vmware.com>
diff --git a/docs/systems.html b/docs/systems.html
index 1192405..7b1d348 100644
--- a/docs/systems.html
+++ b/docs/systems.html
@@ -81,7 +81,7 @@
 <li>DOS
 <li>fbdev
 <li>DEC/VMS
-<ul>
+</ul>
 
 </body>
 </html>