Idomatic-ize example

We don't post-increment hash keys to count things in Perl 6.

Author: zoffixznet

doc/Language/testing.pod6

@@ -402,17 +402,10 @@ use Test;
 plan 1;
 
 sub count-chars(Str() $x) {
-    my %chars;
-    %chars{$_}++ for $x.comb;
-    return %chars;
+    $x.comb.Bag
 }
-my %expected =
-    f   => 1,
-    l   => 1,
-    e   => 3,
-    c   => 1,
-    ;
-is-deeply count-chars('fleece'), %expected, 'count-chars works on "fleece"';
+my $expected = bag <f l e e e c>;
+is-deeply count-chars('fleece'), $expected, 'count-chars works on "fleece"';
 =end code
 
 B<Note:> for L<historical