Update Residence validation

- Update residence_valid? method to don't check :year_of_birth
when :date_of_birth is present.
- Remove unused 'census_year_of_birth' method.

app/models/officing/residence.rb

@@ -117,12 +117,12 @@ class Officing::Residence
     end
 
     def residency_valid?
-      @census_api_response.valid? &&
-        @census_api_response.date_of_birth.year.to_s == year_of_birth.to_s
+      @census_api_response.valid? && valid_year_of_birth?
     end
 
-    def census_year_of_birth
-      @census_api_response.date_of_birth.year
+    def valid_year_of_birth?
+      return true if Setting.force_presence_date_of_birth?
+      @census_api_response.date_of_birth.year.to_s == year_of_birth.to_s
     end
 
     def clean_document_number