mixins.less: Remove user-select() mixin

This has been moved to ipl-web

Author: sukhwinder33445

public/css/icinga/mixins.less

@@ -60,13 +60,6 @@
           transform: @transform;
 }
 
-.user-select(@user-select) {
-  -webkit-user-select: @user-select;
-  -moz-user-select: @user-select;
-  -ms-user-select: @user-select;
-  user-select: @user-select;
-}
-
 .transition (@transition) {
   -webkit-transition: @transition;
      -moz-transition: @transition;