fix(xml): fix screenshot path

Signed-off-by: Stanislas <skita@teclib.com>

Author: stonebuzz

treeview.xml

@@ -101,7 +101,7 @@
          </en>
    </tags>
       <screenshots>
-      <screenshot>https://github.com/pluginsGLPI/treeview/master/master/screenshots/treeview.png</screenshot>
-      <screenshot>https://github.com/pluginsGLPI/treeview/master/master/screenshots/treeview.gif</screenshot>
+      <screenshot>https://raw.githubusercontent.com/pluginsGLPI/treeview/master/screenshots/screenshot.png</screenshot>
+      <screenshot>https://raw.githubusercontent.com/pluginsGLPI/treeview/master/treeview.gif</screenshot>
    </screenshots>
 </root>