[css-step-sizing] Minor editorial

Author: kojiishi

css-step-sizing/Overview.bs

@@ -82,9 +82,6 @@ Adjusting Line Box Heights: the 'line-height-step' property {#line-height-step}
 This property defines the <dfn>step unit</dfn> for line box heights.
 Non-negative <<length>>s are valid.
 
-Stepping Line Box Heights {#height}
------------------------------------
-
 When the <a>step unit</a> is set to a positive <<length>>,
 the line box heights are rounded <i>up</i> to
 the closest multiple of the unit.