Update docs/lxplus/introduction.md

docs/lxplus/introduction.md

 # An introduction
 
-Official documentation: <https://cern.ch/lxplusdoc/>
+Official documentation: <https://lxplusdoc.web.cern.ch/>
 
 LXPLUS, the "Linux Public Login User Service" is the interactive logon service to Linux for all CERN users.
 The cluster LXPLUS consists of public machines provided by the IT Department for interactive work.
 
 You can use SSH to access it from anywhere in the world with your CERN account.
 
-A list of all lxplus aliases can be found at <https://cern.ch/lxplusdoc/evolution/list.html>
+A list of all lxplus aliases can be found at <https://lxplusdoc.web.cern.ch/evolution/list/>
 
 It will be used extensively during this course.