CLDC-1794 Update hint for starter tenancy (#1655)

# Context

- https://digital.dclg.gov.uk/jira/browse/CLDC-1794

# Changes

- Update hint text for lettings 22/23 and 23/24

app/models/form/lettings/questions/startertenancy.rb

@@ -6,7 +6,7 @@ class Form::Lettings::Questions::Startertenancy < ::Form::Question
     @header = "Is this a starter tenancy?"
     @type = "radio"
     @check_answers_card_number = 0
-    @hint_text = ""
+    @hint_text = "This is also known as an ‘introductory period’."
     @answer_options = ANSWER_OPTIONS
     @question_number = 26
   end

config/forms/2022_2023.json

@@ -984,7 +984,7 @@
                 "startertenancy": {
                   "check_answer_label": "Is this a starter or introductory tenancy?",
                   "header": "Is this a starter tenancy?",
-                  "hint_text": "",
+                  "hint_text": "This is also known as an ‘introductory period’.",
                   "type": "radio",
                   "answer_options": {
                     "1": {