Fix incorrect identifiers in PAKE operation example code

[krish2718]

Summary

The SPAKE2+ and WPA3-SAE operation examples in the PAKE chapter
(doc/crypto/api/ops/pake.rst) reference PAKE step macros that are not
defined anywhere in the specification, and the WPA3-SAE shared-key
extraction snippet operates on the wrong operation object. These are
copy/paste-style errors in the .. code-block:: xref example snippets;
they do not affect the normative text or the API.

Fixes

WPA3-SAE example

• The send-confirm counter input step used PSA_PAKE_STEP_SEND_CONFIRM,
  which is undefined. The defined step is PSA_PAKE_STEP_CONFIRM_COUNT
  (0x07), whose documented format is exactly "the 2-byte little-endian
  send-confirm counter".
• psa_pake_get_shared_key() operated on &spake2p_p (left over from the
  SPAKE2+ section) instead of the example's &wpa3_sae operation.

SPAKE2+ example

• The Prover input step for the Verifier confirmation value used
  PSA_PAKE_STEP_KEY_CONFIRM, which is undefined. The defined step is
  PSA_PAKE_STEP_CONFIRM (0x04), consistent with every other
  confirmation step in the same example.

A "Clarifications and fixes" entry is added to the document change history.

Notes

• Documentation only — no normative or API change.
• Found while implementing WPA3-SAE against the 1.4 specification.
• Two commits, split by protocol, so the SPAKE2+ correction can be taken
  or dropped independently of the WPA3-SAE one.
• Both commits are DCO signed-off.