OpenSSL::Test::__fixup_prg: don't check program existence
OpenSSL::Test::__fixup_prg: don't check program existence

The program will fail to run if it doesn't exist anyway, no need to
check its existence here.

Fixes #4306

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4309)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl