fix #13360 by making deprecation notices visible in customizer

less/variables.less

@@ -236,7 +236,7 @@
 //** Text color for headers within dropdown menus.
 @dropdown-header-color:          @gray-light;
 
-// Note: Deprecated @dropdown-caret-color as of v3.1.0
+//** Deprecated `@dropdown-caret-color` as of v3.1.0
 @dropdown-caret-color:           #000;
 
 
@@ -261,28 +261,32 @@
 //## Define the breakpoints at which your layout will change, adapting to different screen sizes.
 
 // Extra small screen / phone
-// Note: Deprecated @screen-xs and @screen-phone as of v3.0.1
-// Note: Deprecated @screen-xs-min as of v3.2.0
+//** 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
-// Note: Deprecated @screen-sm and @screen-tablet as of v3.0.1
+//** Deprecated `@screen-sm` as of v3.0.1
 @screen-sm:                  768px;
 @screen-sm-min:              @screen-sm;
+//** Deprecated `@screen-tablet` as of v3.0.1
 @screen-tablet:              @screen-sm-min;
 
 // Medium screen / desktop
-// Note: Deprecated @screen-md and @screen-desktop as of v3.0.1
+//** Deprecated `@screen-md` as of v3.0.1
 @screen-md:                  992px;
 @screen-md-min:              @screen-md;
+//** Deprecated `@screen-desktop` as of v3.0.1
 @screen-desktop:             @screen-md-min;
 
 // Large screen / wide desktop
-// Note: Deprecated @screen-lg and @screen-lg-desktop as of v3.0.1
+//** Deprecated `@screen-lg` as of v3.0.1
 @screen-lg:                  1200px;
 @screen-lg-min:              @screen-lg;
+//** Deprecated `@screen-lg-desktop` as of v3.0.1
 @screen-lg-desktop:          @screen-lg-min;
 
 // So media queries don't overlap when required, provide a maximum