Remove alt attribute from HTMLObjectElement interface

[benbraou]

alt is not part of the HTML Standard for HTMLObjectElement

Fixes microsoft/TypeScript#21386

[mhegazy]

Can you also remove the comment from https://github.com/Microsoft/TSJS-lib-generator/blob/master/inputfiles/comments.json#L2811

[benbraou]

Done. Thanks!

[mhegazy]

u also need to update the baselines after removing the comment.

[benbraou]

Done. Thanks for taking time to review :) I see now how comments.json and removedTypes.json play together to generate the baseline

[benbraou]

@mhegazy does it make sense to you to update the section inREADME

Add missing elements to inputfiles/addedTypes.json, overriding elements to inputfiles/overridingTypes.json, or elements to remove to inputfiles/removedTypes.json.

with an indication that that may also imply to add/remove comments from inputfiles/comments.json (depending on the matching types that have been added or removed)

I can do a PR for that