Update reference to import SSL certificates

In the following article: Connecting to LDAP or JIRA applications or Other Services via SSL

Under "Importing SSL Certificates" we suggest commands for JDK 1.5 and a documentation for JDK 1.6. However, we only support JDK 1.8 since Confluence 5.8, as per Supported Platforms.

Could we update the documentation with the correct command line and reference for JDK 1.8?

• https://docs.oracle.com/javase/8/docs/technotes/tools/unix/keytool.html

Thanks!