Fix property type of Main Channel of Health plugin
Fix property type of Main Channel of Health plugin

The property type must be DBUS_TYPE_OBJECT_PATH instead
of DBUS_TYPE_STRING. This is in sync with the documentation
and with the other places of usage such as the property change
signal.

pstglia/external-bluetooth-bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,ComputeCycles/bluez,ComputeCycles/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,silent-snowman/bluez,pkarasev3/bluez,mapfau/bluez,mapfau/bluez,silent-snowman/bluez,pkarasev3/bluez,mapfau/bluez,silent-snowman/bluez