doc: Apply more consistently <productname> markup for OpenSSL
OpenSSL was quoted in inconsistent ways in many places of the docs,
sometimes with <application>, <productname> or just nothing.
Author: Daniel Gustafsson
Discussion: https://postgr.es/m/
DA91E5F0-5F9D-41A7-A7A6-
B91CDE0F1D63@yesql.se