RU-OGRN: point to the official FTS register instead of a reseller

[iwdri]

The RU-OGRN entry currently points to a commercial reseller rather than the
official register, and understates data availability. All three points below are
checkable in a browser.

1. url and access.publicDatabase pointed to a reseller

They read https://www.egrul.ru/. That is a paid third-party service, not the
register itself — the entry's own onlineAccessDetails even linked its price
list at russianpartner.biz/tariffs.html.

The official register is maintained by the Federal Tax Service of Russia at
https://egrul.nalog.ru/ — free, no registration, no payment. A search by
OGRN, INN or company name returns an extract as a PDF signed with the FTS
electronic signature.

2. onlineAccessDetails described the reseller's paywall

It stated that registration and per-request payment are required. That is true of
egrul.ru, not of the register. Rewritten to describe the official free service.

3. data.availability was data_not_available — this is incorrect

The Federal Tax Service publishes the full EGRUL and EGRIP as bulk open data at
https://www.nalog.gov.ru/opendata/. Changed to ["bulk", "xml", "pdf"] and
added dataAccessDetails pointing at the open data portal.

Other changes

• description.en rewritten: it was a marketing quotation from the reseller,
  including a claim about "access to foreign state registers of more than 200
  countries", which has nothing to do with the EGRUL.
• access.languages reduced to ["ru"]: the official interface is Russian only.
  The English claim came from the reseller.

Notes

The entry has not been touched since 2017 (meta.source: "ProZorro Business
Register Research"), which explains the drift.

I am aware the README says unsolicited new entries are not being accepted. This
is not a new entry — it is a factual correction to an existing one, and I have
added no new links to my own or any other commercial service.

Disclosure: I work on a Russian company-data service, so I read this entry
closely. That is also why I have kept this PR to correcting the official source
only.