Update how form answer PDFs are rendered for supporters question

[DaniBitZesty]

📝 A short description of the changes

• Letters of support questions are structured as 1 question with 2 entities. The support letters are stored within a supporter_letters_list array:

 document:
  {
   "supporter_letters_list"=>
      [
        {"support_letter_id"=>"",
         "first_name"=>"",
         "last_name"=>"",
         "relationship_to_nominee"=>"",
         "letter_of_support"=>""},
       {"support_letter_id"=>"",
         "first_name"=>"",
         "last_name"=>"",
         "relationship_to_nominee"=>"",
         "letter_of_support"=>""}
]...

• Because the PDF generator will interpret this as one question, I am 'mocking' the question refs (C 1.1) so that the PDF version of the question looks like this:

C1. The first letter of support
C1.1. Name of the person who wrote the first letter of support

First name:

Surname:

C1.2. Relationship to group
For example, a beneficiary of the group, local resident or member of a partner charity.

C1.3. Upload the first letter of support

🔗 Link to the relevant story (or stories)

Deployment implications

✅ Checklist

• Features that cannot go live are behind a feature flag/env var or specify deploy date and open PR as draft
• I have checked that commit messages make sense and explain the reasoning for each change
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have squashed any unnecessary or part-finished commits

🖼️ Screenshots (if appropriate - no PII/Prod data):