Remove TODO comments about Check patient has at least one "sufficient" identifier

Issues from TODOs

Line 296 - 299 of PatientServiceImpl.java
Link: https://github.com/openmrs/openmrs-core/blob/6483ffff986636fb754bb36b46e753c5b97c2461/api/src/main/java/org/openmrs/api/impl/PatientServiceImpl.java#L296

Contains the TODO
check patient has at least one "sufficient" identifier
what makes a patient identifier unique ... can you have the
same identifier number at different locations? if so, then this
check duplicate algorithm does not handle this case