fix: Fix code editor becoming hidden when the group is focused

[avinashbot]

Description

I don't think it's supposed to do that:

Not sure when it happened, but we are colliding with ace's wrapper div for styling here. I assume the intent was always to have position: absolute, but I don't know if it ever worked with the mixin's position: relative overriding that anyway. So I moved those declarations to after the mixin.

Related links, issue #, if available: AWSUI-60262

How has this been tested?

Local testing, but I suppose a screenshot test is in order.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.40%. Comparing base (1c32dd6) to head (cbdd42a).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3174    +/-   ##
========================================
  Coverage   96.40%   96.40%            
========================================
  Files         784      784            
  Lines       22143    22143            
  Branches     7604     7192   -412     
========================================
  Hits        21348    21348            
- Misses        743      788    +45     
+ Partials       52        7    -45     

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