[css-overflow-4] Clarify interaction between block-ellipsis and nowrap

See w3c#12811

Author: frivoal

css-overflow-4/Overview.bs

@@ -787,7 +787,8 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 	and is placed in the line box after the last
 	<a>soft wrap opportunity</a> (see [[!CSS-TEXT-3]])
 	that would still allow the entire <a>block overflow ellipsis</a> to fit on the line.
-	For this purpose, <a>soft wrap opportunities</a> added by 'overflow-wrap' are ignored.
+	For this purpose, <a>soft wrap opportunities</a> added by 'overflow-wrap' are ignored,
+	as are those inhibited by ''text-wrap-mode: nowrap''.
 	If this results in the entire contents of the line box being displaced,
 	the line box is considered to contain a [=strut=], as defined in [[CSS2/visudet#leading]].
 	Text <a href="https://www.w3.org/TR/css-text-3/#justification">alignment and justification</a>