secret-session: Avoid double-free in service_encode_plain_secret()
secret-session: Avoid double-free in service_encode_plain_secret()

As g_variant_builder_add_value() takes ownership of a floating
GVariant, we don't need to unref it afterwards.

GNOME/libsecret,GNOME/libsecret,GNOME/libsecret,GNOME/libsecret