Avoid using gets as an argument name in a prototype

Avoid using gets as an argument name in a prototype

This otherwise breaks compilation of applications using ssl.h on MingW.

Fixes #22296

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22316)