LG-7686: Update address line 2 label for IPP address form

[aduth]

🎫 Ticket

LG-7686

🛠 Summary of changes

Updates "Address (optional)" to "Address line 2 (optional)" in the in-person proofing address form, for clarity and consistency with unsupervised flow step labels updated in #7180 (LG-7669).

📜 Testing Plan

1. Go to http://localhost:3000
2. Sign in
3. Go to http://localhost:3000/verify
4. Complete proofing flow up to document capture
5. Use attention result test document for front and back
6. Submit
7. Enter in-person proofing flow and complete up to address form
8. Observe that the label for second address line is "Address line 2 (optional)"

👀 Screenshots

Screen	Before	After
Form
Verify step

[zachmargolis]

LGTM

[lizzieamanning]

LGTM!