[css-ui-4] Avoid using the same name for different types, it's confusing

Part of w3c#2466

Author: frivoal

css-ui-4/Overview.bs

@@ -399,7 +399,7 @@ Animation type: <a href="https://drafts.csswg.org/css3-transitions/#animtype-len
 
 <pre class="propdef">
 Name: outline-style
-Value: auto | <<outline-style>>
+Value: auto | <<outline-line-style>>
 Initial: none
 Applies to: all elements
 Inherited: no
@@ -456,7 +456,7 @@ The 'outline-width' property accepts
 the same values as 'border-width'
 ([[css-backgrounds-3#the-border-width]]).
 
-<dfn><<outline-style>></dfn> accepts
+<dfn><<outline-line-style>></dfn> accepts
 the same values as <<line-style>>
 ([[css-backgrounds-3#the-border-style]])
 with the same meaning,