[css-text-3] correct path to test file

Author: frivoal

css-text-3/Overview.bs

@@ -1104,9 +1104,9 @@ Characters and Letters</h3>
 
       <wpt pathprefix="/css/CSS2/text/">
         white-space-008.xht
-        white-space-process-016.xht
-        white-space-process-017.xht
-        white-space-process-018.xht
+        white-space-processing-016.xht
+        white-space-processing-017.xht
+        white-space-processing-018.xht
       </wpt>
 
       <p>For other values of 'white-space', <a>segment breaks</a> are <a>collapsible</a>.