[css-ruby-1] Clarify that we're talking about collapsing across consecutive elements

Author: fantasai

css-ruby-1/Overview.bs

@@ -626,7 +626,8 @@ White Space Collapsing</h3>
 			&lt;/ruby></pre>
 	</div>
 
-	Where undiscarded white space is [=collapsible white space|collapsible=], it will collapse
+	Where undiscarded white space is [=collapsible white space|collapsible=],
+	it will collapse across consecutive elements
 	following the standard <a href="https://www.w3.org/TR/css3-text/#white-space-rules">white space processing rules</a>. [[!CSS3TEXT]]
 	For [=collapsible white space=] between [=ruby segments=] ([=inter-segment white space=]), however,
 	the contextual text for determining collapsing behavior is given by the [=ruby bases=] on either side,