[GR-17457] Make array/flatten-recursive micro benchmark compatible with JRuby.

PullRequest: truffleruby/2118

Author: Nicolas Laurent

bench/micro/array/flatten-recursive.rb renamed to bench/micro/array/flatten-deep.rb

@@ -10,10 +10,10 @@
 current_array = array
 100.times do
   next_array = []
-  current_array.append(0, 1, next_array, 3, 4)
+  current_array.concat [0, 1, next_array, 3 , 4]
   current_array = next_array
 end
 
-benchmark 'core-array-flatten-recursive' do
+benchmark 'core-array-flatten-deep' do
   array.flatten
 end