Update x-window-system.md - removed trivial links

docs.it4i/general/accessing-the-clusters/graphical-user-interface/x-window-system.md

 # X Window System
 
-The X Window system is a principal way to get GUI access to the clusters. The **X Window System** (commonly known as **X11**, based on its current major version being 11, or shortened to simply **X**, and sometimes informally **X-Windows**) is a computer software system and network [protocol][a] that provides a basis for [graphical user interfaces][b] (GUIs) and rich input device capability for [networked computers][c].
+The X Window system is a principal way to get GUI access to the clusters. The **X Window System** (commonly known as **X11**, based on its current major version being 11, or shortened to simply **X**, and sometimes informally **X-Windows**) is a computer software system and network protocol that provides a basis for graphical user interfaces (GUIs) and rich input device capability for networked computers.
 
 !!! tip
     The X display forwarding must be activated and the X server running on client side
@@ -156,9 +156,6 @@ Use System-Log Out to close the gnome-session.
 [2]: #putty-on-windows
 [3]: #wsl-bash-on-windows
 
-[a]: http://en.wikipedia.org/wiki/Protocol_%28computing%29
-[b]: http://en.wikipedia.org/wiki/Graphical_user_interface
-[c]: http://en.wikipedia.org/wiki/Computer_network
 [d]: https://www.xquartz.org
 [e]: http://sourceforge.net/projects/xming/
 [f]: http://x.cygwin.com/