[css-display] fix markup error

Author: tabatkins

css-display/Overview.bs

@@ -276,11 +276,11 @@ Outer Display Roles for Flow Layout: the ''block'', ''inline'', and ''run-in'' k
 	<dl dfn-type="value" dfn-for="display, <display-outside>">
 		<dt><dfn>block</dfn>
 		<dd>
-			The element generates a <dfn dfn>block-level box</dfn>. [[!CSS2]]
+			The element generates a <dfn dfn for>block-level box</dfn>. [[!CSS2]]
 
 		<dt><dfn>inline</dfn>
 		<dd>
-			The element generates an <dfn dfn>inline-level box</dfn>. [[!CSS2]]
+			The element generates an <dfn dfn for>inline-level box</dfn>. [[!CSS2]]
 
 		<dt><dfn>run-in</dfn>
 		<dd>
@@ -304,7 +304,7 @@ Inner Display Layout Models: the ''flow'', ''flow-root'', ''table'', ''grid'', a
 	<dl dfn-type="value" dfn-for="display, <display-inside>">
 		<dt><dfn>flow</dfn>
 		<dd>
-			The element lays out its contents using <dfn dfn>flow layout</dfn>
+			The element lays out its contents using <dfn dfn for>flow layout</dfn>
 			(<a href="https://www.w3.org/TR/CSS2/visuren.html">block-and-inline layout</a>).
 
 			If its <a>outer display type</a> is ''inline'' or ''run-in'',
@@ -394,14 +394,14 @@ Layout-Internal Display Types: the ''table-*'' and ''ruby-*'' keywords</h3>
 	<dl dfn-type=value dfn-for="display, <display-internal>">
 		<dt><dfn>table-row-group</dfn>, <dfn>table-header-group</dfn>, <dfn>table-footer-group</dfn>, <dfn>table-row</dfn>, <dfn>table-cell</dfn>, <dfn>table-column-group</dfn>, <dfn>table-column</dfn>, <dfn>table-caption</dfn>
 		<dd>
-			The element is an <dfn dfn>internal table element</dfn>,
+			The element is an <dfn dfn for>internal table element</dfn>,
 			and participates in a table layout context. [[!CSS2]]
 
 			''table-cell'' and ''table-caption'' have a ''flow-root'' <a>inner display type</a>.
 
 		<dt><dfn>ruby-base</dfn>, <dfn>ruby-text</dfn>, <dfn>ruby-base-container</dfn>, <dfn>ruby-text-container</dfn>
 		<dd>
-			The element is an <dfn dfn>internal ruby element</dfn>,
+			The element is an <dfn dfn for>internal ruby element</dfn>,
 			and participates in a ruby layout context. [[!CSS3RUBY]]
 
 			''ruby-base'' and ''ruby-text'' have a ''flow'' <a>inner display type</a>.