Combining charts leads to tag duplication #374

Description

When combining charts using Chart.combine or Chart.Grid, title, meta and link tags in the html head are duplicated.

Repro steps

Please provide the steps required to reproduce the problem

1. Generate combined chart

#r "nuget: Plotly.NET, 4.0.0"

open Plotly.NET

[
    Chart.Point([1,2])
    Chart.Point([1,2])
]
|> Chart.combine
|> Chart.show

3. Look at the html