be more precise about return types of sub await

Author: gfldex

doc/Type/Promise.pod6

@@ -252,11 +252,12 @@ or C<quit> with the C<cause> if the L<Promise> is Broken.
 
 =head2 sub await
 
-    multi sub await(Promise:D)
-    multi sub await(*@)
+    multi sub await(Promise:D --> Promise)
+    multi sub await(*@ --> Array)
 
 Waits until one or more promises are I<all> fulfilled, and then returns their
 values. Also works on L<channels|/type/Channel>. Any broken promises will
-rethrow their exceptions.
+rethrow their exceptions. If a list of promises is provided a list of promises
+is returned.
 
 =end pod