Update EVP_VerifyInit.pod

Method name correction.

CLA: trivial

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/9052)

(cherry picked from commit 3c9a8d4a)