update form field names to match calendly form

[midigofrank]

Description

This PR updates the book demo form fields to match those used in calendly

Validation steps

This should be validated from the billing app

AI Usage

Please disclose how you've used AI in this work (it's cool, we just want to know!):

• Code generation (copilot but not intellisense)
• Learning or fact checking
• Strategy / design
• Optimisation / refactoring
• Translation / spellchecking / doc gen
• Other
• I have not used AI

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Pre-submission checklist

• I have performed a self-review of my code.
• I have implemented and tested all related authorization policies. (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.21%. Comparing base (9763a32) to head (5affbe1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3076   +/-   ##
=======================================
  Coverage   91.21%   91.21%           
=======================================
  Files         356      356           
  Lines       13153    13153           
=======================================
  Hits        11998    11998           
  Misses       1155     1155           

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