Update more diagnostic messages ES6->2015

[Texas Toland (texastoland)]

Fix #8996 CC Mohamed Hegazy (@mhegazy).

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[Texas Toland (texastoland)]

Passed locally I must need to rebase…

[Mohamed Hegazy (mhegazy)]

thanks!

[Mohamed Hegazy (mhegazy)]

For future references, files under lib\ are generated by jake LKG, and not updated in PRs.

[Texas Toland (texastoland)]

Curious because those did look generated. So they're not intended to be versioned?

[Mohamed Hegazy (mhegazy)]

We refresh them regularly. but off master.

[Texas Toland (texastoland)]

Makes sense thanks!