[openssl/openssl] 7f7918: Documenting lack of error codes stability

[Dmitry Belyavskiy]

  Branch: refs/heads/openssl-3.1
  Home:   https://github.com/openssl/openssl
  Commit: 7f7918e92440ad1aec7a773dd249a419019e96d7
      https://github.com/openssl/openssl/commit/7f7918e92440ad1aec7a773dd249a419019e96d7
  Author: Dmitry Belyavskiy <beldmit at gmail.com>
  Date:   2023-01-16 (Mon, 16 Jan 2023)

  Changed paths:
    M doc/man3/ERR_GET_LIB.pod

  Log Message:
  -----------
  Documenting lack of error codes stability

Reviewed-by: Hugo Landau <hlandau at openssl.org>
Reviewed-by: Matt Caswell <matt at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20019)

(cherry picked from commit ae61bd34e676036f22e44e8184d1ba649a990619)