Improve BagHash.new examples

[zoffixznet]

https://irclog.perlgeek.de/perl6-dev/2017-10-25#i_15352349

15:57 | jnthn | m: my $n = BagHash.new: "a" => 0, "b" => 1, "c" => 2, "c" => 2; say $n.perl
-- | -- | --
15:57 | camelia | rakudo-moar 97b11edd6: OUTPUT: «(:c(2)=>2,:b(1),:a(0)).BagHash␤»
15:57 | jnthn | m: my $n = BagHash.new-from-pairs: "a" => 0, "b" => 1, "c" => 2, "c" => 2; say $n.perl
15:57 | camelia | rakudo-moar 97b11edd6: OUTPUT: «("b","c"=>4).BagHash␤»
15:58 | jnthn | It might be less confusing if the .new example at https://docs.perl6.org/type/BagHash#Creating_BagHash_objects didn't use pairs that look like they'll be providing weights as its first example