fix country drawer for small choices

[francoispeyret]

PR Summary:

QuickFix to next issue.

Issue reference

The country selector's height with not many countries on it feels a bit overwhelming on mobile in the menu drawer. (Video reference)

My fix :

Why are these changes introduced?

Fixes #3252 .

What approach did you take?

Minimum code modification for fix the issue.

Visual impact on existing themes

If the country's choice is small the drawer was small too and the height was limited at 80% of screen's height.

Checklist

• Added PR summary for release notes
• Requested review from UX (Only for changes that are affecting the experience or perceivable visual details)
• Created a ticket for the help.shopify.com documentation team about updates to theme settings. (Internal-only task)
• Followed theme code principles
• Linted with Theme Check
• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility