Fix hint text

Previously the hint text was showing all subjects to claimants, even if
they were not eligible for those subjects, instead only show subjects
the claimant is eligible for. If the claimant is not eligible for any
subjects they will have been kicked out of the journey prior to this
screen.

app/helpers/claims/itt_subject_helper.rb

@@ -1,7 +1,10 @@
 module Claims
   module IttSubjectHelper
     def subjects_to_sentence_for_hint_text(answers)
-      all_ecp_subjects = [:chemistry, :foreign_languages, :mathematics, :physics]
+      all_ecp_subjects = Policies::EarlyCareerPayments.subject_symbols(
+        claim_year: answers.policy_year,
+        itt_year: answers.itt_academic_year
+      )
       all_lup_subjects = Policies::LevellingUpPremiumPayments.fixed_subject_symbols
 
       hint_subject_symbols = Set[]

spec/helpers/claims/itt_subject_helper_spec.rb

@@ -94,7 +94,8 @@
         build(
           :additional_payments_answers,
           :lup_ineligible,
-          :ecp_eligible_later
+          :ecp_eligible_later,
+          itt_academic_year: AcademicYear.new(2020)
         )
       end