Decrease onresize debounce from 100ms to 10ms

The debounce is trailing, not leading/throttled. This means
the value doesn't decide how often it runs while the user is
resizing. It decides how long after they stop resizing will
it first run.

Given the calculation isn't super expensive, a much lower value
should suffice. The main thing we want is that while the user
is actively resizing and 100s of events are queued up (faster than
JS can process), that we wait until the end of the chain before
computing it (once). If the user actually stops moving, even for
a little bit, that little bit however small should be more than
long enough for a repaint to take place.

Test Plan:
* Open two tabs, one after checking out master, and
  one after checking out this patch. Make sure you are logged-in
  on MW as an administrator user (to get more tabs).
* Verify that `mw.loader.getVersion('skins.vector.js')` returns
  different values from the console for each.
* Resize the window from wide to very narrow and back.
  Before, the tab bar updates relatively late it feels sluggish.
  After, the tab bar appears to update as/while you let go.

Change-Id: If02338559abc71668d0655e8b3be1a5f73e646a9

collapsibleTabs.js

@@ -50,7 +50,7 @@
 		// if we haven't already bound our resize handler, bind it now
 		if ( !boundEvent ) {
 			boundEvent = true;
-			$( window ).on( 'resize', mw.util.debounce( 100, function () {
+			$( window ).on( 'resize', mw.util.debounce( 10, function () {
 				rAF( $.collapsibleTabs.handleResize );
 			} ) );
 		}