[NP] Get rid of ui/i18n in Discover

[maryia-lapata]

Summary

Part of #60097.

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• This was checked for keyboard-only and screenreader accessibility
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser
• This was checked for cross-browser compatibility, including a check against IE11

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: c055d82

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[kertal]

@maryia-lapata thx! ACK, will review today

[maryia-lapata]

Duplicate line.

[kertal]

thx for cleaning this up !

[flash1293]

Tested and couldn't find any problems, LGTM.

A side note: To also have phrases within EUI components translated properly (e.g. for the EuiBasicTable component), everything should theoretically be wrapped into a I18nContext returned from core.i18n.Context. In this particular case I couldn't find an instance of this, so this looks good to me for now (especially since passing down the context component will be a lot of work as they are a lot of roots).

When we are denagularizing the rest of the application, it will be sufficient to place a single I18nContext in the root of the react app.

[kertal]

Code LGTM 👍 , thx for the cleanups! Tested locally in Chrome 80, macOs 10.14.6
✅ Discover Main
✅ Discover Context
✅ Discover Doc view
All work as expected