I would use comments, but cannot paste the formatted code there. I will edit my answer if necessary.

I think you can't fetch your map like in your example. I was able to get your map this way:

indiageojson <- content(GET(""))
indiageojson <- jsonlite::fromJSON(indiageojson)
indiageojson <- geojsonio::as.json(indiageojson)
highchart(type = "map") %>%
  hc_add_series(mapData = indiageojson)

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