[css-inline-3] Rename invisible line boxes to phantom line boxes

This lines up closer to CSS2 terminology.

Related to #11021

css-inline-3/Overview.bs

@@ -246,15 +246,15 @@ Layout Within Line Boxes</h3>
 	and thus influence these calculations just like boxes with content.
 
 <h3 id="invisible-line-boxes">
-“Invisible” Line Boxes</h3>
+Phantom Line Boxes</h3>
 
 	[=Line boxes=] that contain no text,
 	no [=preserved white space=],
 	no [=inline boxes=] with non-zero inline-axis [=margins=], [=padding=], or [=borders=],
 	and no other [=in-flow=] content
 	(such as [=atomic inlines=] or [=ruby annotations=]),
 	and do not end with a [=forced line break=]
-	are <dfn lt="invisible line box">invisible line boxes</dfn>.
+	are <dfn lt="phantom line box">phantom line boxes</dfn>.
 	Such boxes must be treated as zero-[=logical height|height=] [=line boxes=]
 	for the purposes of determining the positions of any descendant content
 	(such as [=absolutely positioned boxes=]),
@@ -264,16 +264,17 @@ Layout Within Line Boxes</h3>
 	<details class=note>
 		<summary>What’s invisible?</summary>
 
-		Such [=invisible line boxes=], which can still contain
+		Such [=phantom line boxes=], which can still contain
 		unstyled empty [=inline boxes=], [=out-of-flow=] boxes, and/or collapsed [=document white space=],
 		are ignored, for example, for:
 		* <a href="https://www.w3.org/TR/CSS2/box.html#collapsing-margins">margin collapsing</a>
 		* finding the [=first formatted line=]
 		* applying 'text-box-trim'
 		* [[css-break-4#break-propagation|fragmentation break propagation]]
+		* etc.
 	</details>
 
-	ISSUE: Firefox allows the inline boxes within an [=invisible line box=]
+	ISSUE: Firefox allows the inline boxes within a [=phantom line box=]
 	to accept 'outline',which allows it to make focus rings visible.
 	As in other browsers, all other properties that could make the element visible
 	(e.g. 'box-shadow')
@@ -3076,7 +3077,7 @@ Changes</h2>
 			when calculating their [=layout bounds=]
 			so that they can actually have the specified effect.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/8182">Issue 8182</a>)
-		<li>Corrected [=invisible line boxes=] to only account for [=inline-axis=] box decorations.
+		<li>Corrected [=phantom line boxes=] to only account for [=inline-axis=] box decorations.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/9344">Issue 9344</a>)
 	</ul>