Broken example in `print_tree` docstring

[joshday]

Docstring:

julia> print_tree(stdout, Dict("a"=>"b","b"=>['c','d']))
Dict{String,Any}("b"=>['c','d'],"a"=>"b")
├─ b
│  ├─ c
│  └─ d
└─ a
   └─ b

Actual:

julia> print_tree(stdout, Dict("a"=>"b","b"=>['c','d']))
Dict{String,Any}
├─ Array{Char,1}
│  ├─ 'c'
│  └─ 'd'
└─ "b"