Drop: @screen-xs, @screen-xs-min, and @screen-phone

less/navbar.less

@@ -92,7 +92,7 @@
   .navbar-collapse {
     max-height: @navbar-collapse-max-height;
 
-    @media (max-device-width: @screen-xs-min) and (orientation: landscape) {
+    @media (max-device-width: 480px) and (orientation: landscape) {
       max-height: 200px;
     }
   }

less/variables.less

@@ -261,12 +261,6 @@
 //## Define the breakpoints at which your layout will change, adapting to different screen sizes.
 
 // Extra small screen / phone
-//** Deprecated `@screen-xs` as of v3.0.1
-@screen-xs:                  480px;
-//** Deprecated `@screen-xs-min` as of v3.2.0
-@screen-xs-min:              @screen-xs;
-//** Deprecated `@screen-phone` as of v3.0.1
-@screen-phone:               @screen-xs-min;
 
 // Small screen / tablet
 //** Deprecated `@screen-sm` as of v3.0.1