Drill down to org->gnome->desktop->remote-access and uncheck the box.
The only option is to disable the requirement for encryption. Load and run the dconf-editor; but only after stopping any running vino-server:
The following information was collected from Fedora 21 (Gnome 3.14) and OS X 10.10 (Yosemite).
Around Gnome 3.10 release, the VNC Server called Vino that is built into Gnome changed a default value where encryption authentication is now required. Vino uses gnutls library for this encryption had advertises "TLS" encryption but they use anonymous authentication instead of X.509 certification authentication that TigerVNC and RealVNC use. Apple's Screen Sharing app uses EAS-256 encryption and so has no real change of working.
Enabling Screen Sharing under OS X will automatically make OS X visible under Fedora's "Remote Desktop Viewer" app. The Find option under Connect will find the OS X machines advertising Screen Sharing support and you can connect to them using Username/Password values from the OS X machines.
The following will let you see Fedora box in Finder and mount Linux home directories. You can also add additional share points. Any share point can be used as locations for Time Machine backups.
You'll want the contents at bottom to look something like this. Here, I added 'noadouble' to :DEFAULT: line to stop all these annoying dot directories from being created. I also specified a location to store Time Machine backups. Note the "tm" option. This is required if you want to TimeMachine to automatically see this share without resorting to updating an OS X preference to show unsupported network volumes.
And last, a modification to /etc/netatalk/afpd.conf is needed. In older Fedora/OSX combo's, this step wasn't needed. It seems by default DHX2 security module requires PAM to be set up but most default Fedora boxes are using /etc/passwd for storage. So connections will fail because of no password access. Edit /etc/netatalk/afpd.conf and add this line to force DHX2 to look for passwords in /etc/passwd.