Trial flow: Change telephone input field type

What does this MR do?

Changes telephone input field type to improve form completion on mobile. As detailed in Step 1 of #325060 (closed)

Screenshots (strongly suggested)

Before	After
Using <input type="text">	Using <input type="tel">

Note: <input type="tel"> Cross-browser compatibility is good according to Can I use?, is widely supported by assistive technology.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • [-] I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
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• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team