[BUG]: Chart Studio references need to be removed

[camdecoster]

Description

Chart Studio references are present in the library but Chart Studio is now end of life and these should be removed.

Notes

• Here's one example, but there are more:
  

  plotly.js/src/plot_api/plot_schema.js

  Line 553 in 1a52bbc

  description: 'Sets the source reference on Chart Studio Cloud for `' + attrName + '`.',

• Chart Studio is referenced in a number of locale files

[alexcjohnson]

For v4 can we get rid of the *src attributes entirely? AFAIK they have no purpose outside of Chart Studio, so at this point they're just a source of confusion and bloat.