[icons] Remove es folder

[mgansler]

• I have followed (at least) the PR section of the contributing guide.

[oliviertassinari]

@mgansler What problem are you trying to solve? (notice that we keep the master branch for important bugs only, on going work is done the next branch)

[mgansler]

@oliviertassinari see related issue #14517

[oliviertassinari]

@mgansler Thank you! #14517 (comment)

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If you don't mind, I would like to repurpose this pull request to reapply #12662. It seems this change was lost: https://packagephobia.now.sh/result?p=%40material-ui%2Ficons%404.0.0-alpha.0.

[mgansler]

@oliviertassinari I don't think it got lost, the package.json looks good to me. But I just copied the bits from the core package copy-files script to this one. I removed the line to copy the definitions file to the es/ directory.

[eps1lon]

@mgansler This should be fixed on next. Could you test with @material-ui/icons@next and report back what issue you have with the type declarations?

I'm not even sure we should publish typings for that one. I'm not sure if this is part of the public API.
Well issue #13974 and PR #13994 were accepted so they are indeed public. The publish script just never picked those up.

thanks