fix: hides title for Buy screen

[chrisduma-ledger]

✅ Checklist

• npx changeset was attached.
• Covered by automatic tests.
• Impact of the changes:
  • Buy screen title should not be shown anymore

📝 Description

Does not show the default title that comes with React Navigation when navigating to the Buy screen.

❓ Context

• Ticket

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🧐 Checklist for the PR Reviewers

• The code aligns with the requirements described in the linked JIRA or GitHub issue.
• The PR description clearly documents the changes made and explains any technical trade-offs or design decisions.
• There are no undocumented trade-offs, technical debt, or maintainability issues.
• The PR has been tested thoroughly, and any potential edge cases have been considered and handled.
• Any new dependencies have been justified and documented.
• Performance considerations have been taken into account. (changes have been profiled or benchmarked if necessary)

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5 Ignored Deployments

Name	Status	Preview	Comments	Updated (UTC)
ledger-live-docs	⬜️ Ignored (Inspect)			May 23, 2024 7:41pm
ledger-live-github-bot	⬜️ Ignored (Inspect)			May 23, 2024 7:41pm
native-ui-storybook	⬜️ Ignored (Inspect)			May 23, 2024 7:41pm
react-ui-storybook	⬜️ Ignored (Inspect)			May 23, 2024 7:41pm
web-tools	⬜️ Ignored (Inspect)			May 23, 2024 7:41pm