Update the IIS KB(SSL)

Currently, the IIS documentation doesn't have any traces of how to configure Confluence with IIS in a secure zone(SSL).

It would be interesting to add a small section showing to use the following configuration:

• proxyPort="443"
• scheme ="https"

Right now, the documentation is only showing the following configuration:

• proxyPort="80"
• scheme ="http"

Documentation link: https://confluence.atlassian.com/kb/proxying-atlassian-server-applications-with-microsoft-internet-information-services-iis-833931378.html