Remove remaining traces of Rand_OpenSSL() from the tree
fe0a0b5 has removed the last use of this routine from pgcrypto, leading
to a useless symbol definition and an extra configure check.
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson, Tom Lane
Discussion: https://postgr.es/m/
20190626142544.GN1714@paquier.xyz