Update recurring contribution - prevent 'Financial Type is required field' validation error

Donors can do self-service updates of their recurring contributions.

The PHP makes the Financial Type field 'is required', but then the TPL excludes the field when it is being used in the self-service mode. So the form fails validation in this case.

The change is to make the field non-mandatory in self-service mode. This is safe because Financial Type is mandatory for contributions, so it will have a non-NULL value before the form is displayed.