Many README "Chart Example" links are dead/broken

[zkornbluth]

All of the links in that column labeled "Excel" open to https://plotly.com/chart-studio-help/ which is a default docs site, not the chart example. A few others have a 404 Not Found Error or are completely dead.

Full list of broken links:

Link	Error Type
http://help.plot.ly/excel/grouped-bar-chart/	Default docs site
http://help.plot.ly/excel/bubble-chart/	Default docs site
http://help.plot.ly/excel/three-y-axes/	Default docs site
http://help.plot.ly/excel/dot-plots/	Default docs site
https://plotly.com/python/streaming-bubbles-tutorial/	404 Error
http://help.plot.ly/excel/insets	Default docs site
http://help.plot.ly/excel/text-scatter-chart	Default docs site
http://help.plot.ly/excel/LaTeX	Default docs site
http://help.plot.ly/excel/graph-with-multiple-axes/	Default docs site
http://help.plot.ly/excel/heatmap	Default docs site
http://help.plot.ly/excel/pareto-chart	Default docs site
https://dash-bio.plotly.host/dash-clustergram/	Dead link
http://help.plot.ly/excel/shaded-region-on-chart	Default docs site
http://help.plot.ly/excel/insets	Default docs site
http://help.plot.ly/excel/subplots	Default docs site
http://help.plot.ly/excel/time-series	Default docs site
https://plot.ly/pandas/time-series/	404 Error
https://plot.ly/pandas/3d-surface-plots/	404 Error
https://plot.ly/pandas/error-bars/	404 Error