[css-text-3] Wrt trailing spaces and bidi, add cross-reference and ma…

…ke implication informative, rather than declaring a special-case rule. Update to #4308

css-text-3/Overview.bs

@@ -1778,6 +1778,7 @@ Order of Operations</h4>
           white-space-processing-040.xht
           white-space-processing-041.xht
         </wpt>
+
       <li>If the [=tab size=] is zero, [=preserved=] [=tabs=] are not rendered.
         Otherwise, each [=preserved=] [=tab=] is rendered as a horizontal shift
         that lines up the start edge of the next glyph with the next <a>tab stop</a>.
@@ -1835,11 +1836,10 @@ Order of Operations</h4>
           white-space-processing-047.xht
         </wpt>
 
-        In the case of bidirectional text,
-        any sequence of [=collapsible=] [=spaces=] located at the end of the line
+        Note: Due to [[UAX9]] rule <a href="http://unicode.org/reports/tr9/#L1">L1</a>,
+        a 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.
+        will also be at the end of the line after reordering.
 
         <wpt>
           white-space/eol-spaces-bidi-001.html