Do not account for Row size when noheader is set to true

[ronisbr]

When printing a table with the row column and without the header, we should not take into account the size of Row to align the row column:

julia> v = 0:1:6
0:1:6

julia> pretty_table(v;noheader = true, show_row_number = true)
┌─────┬───┐
│   1 │ 0 │
│   2 │ 1 │
│   3 │ 2 │
│   4 │ 3 │
│   5 │ 4 │
│   6 │ 5 │
│   7 │ 6 │
└─────┴───┘