community/geary: depend on gnome-keyring

Otherwise will start fail with:

geary[NET|SER|REP|CNV|PER]: application-controller.vala:348: Error opening libsecret: The name org.freedesktop.secrets was not provided by any .service files

Could be probably provided by another service, but let's default to one that works.

Signed-off-by: David Heidelberg david@ixit.cz