[css-text-3] Used consistent wording to talk about sequences of collapsible spaces in phase 2

Author: frivoal

css-text-3/Overview.bs

@@ -1632,7 +1632,7 @@ Text Processing</h3>
         </wpt>
 
         In the case of bidirectional text,
-        any [=collapsible=] [=space=] located at the end of the line
+        any sequence of [=collapsible=] [=spaces=] located at the end of the line
         prior to <a href="https://www.w3.org/TR/css-writing-modes/#text-direction">bidi reordering</a> [[CSS-WRITING-MODES-3]]
         is also removed,
         and bidi reordering is applied on the remaining content of the line.