Add missing void arg to fix MacOS builds

[alcaeus]

Upgraded to MacOS 13.3 recently and building the driver exposed this failure. Not sure why this didn't appear earlier as strict-prototypes was part of our developer build flags for a long time already.

src/phongo_client.c:78:44: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
const char* php_phongo_crypt_shared_version()