build: Remove build with ssh component from default build instructions

The SSH functionality of gnome-keyring has been moved to gcr as part of the modular gnome-keyring Fedora change proposal. And currently the SSH functionality is provided by gcr-ssh-agent. So, it is recommended to build gnome-keyring without the ssh component.

To summarize, why do we need this change now,

• This sends a strong/valid message that the use of gcr-ssh-agent is recommended and not the gnome-keyring ssh component.
• Arch Linux already recommends the use of gcr-ssh-agent instead of gnome-keyring ssh component.
• This change will prompt other destros (GNOME OS, Debian, Fedora, ...) to update their default gnome-keyring build instructions as well.