[openssl/openssl] 66b2df: Fix typo in base provider example code

[HansHoogerwerf]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: 66b2df32e13ab83125eb1f3ad645fa0400403ff9
      https://github.com/openssl/openssl/commit/66b2df32e13ab83125eb1f3ad645fa0400403ff9
  Author: HansHoogerwerf <hans3132 at live.nl>
  Date:   2023-03-03 (Fri, 03 Mar 2023)

  Changed paths:
    M doc/man7/provider-base.pod

  Log Message:
  -----------
  Fix typo in base provider example code

CLA: trivial

Reviewed-by: Richard Levitte <levitte at openssl.org>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20411)

(cherry picked from commit 08a11ba20461ce14b0a6b9c9e374fbea91fbd8cf)