Fix left behind "async" (we only do "start" now)

Author: lizmat

S02-bits.pod

@@ -4789,7 +4789,7 @@ forces parallel evaluation of any iterator, hyper, or junction, such
 that if any single thread dies or hangs its computation, it does not
 block any other thread from returning its results to the race list.
 When the demand for the race list drops, hung threads may be killed.
-You can think of it as a C<gather> with a 'C<try take async {...}>'
+You can think of it as a C<gather> with a 'C<try take start {...}>'
 on parallel computation.  Note that exceptions are trapped by
 default; if your car crashes, you simply do not finish the race.
 If you want notifications of some sort back to the pit crew, you'll