fix(jsx-curly-brace-presence): do not flag empty string literals in JSX children

[ordinary9843]

When {""} or {''} appears in JSX children and the children option is set to never, the rule reports it as an unnecessary curly brace and auto-fixes it by removing the expression entirely. This changes the JSX tree — an empty string literal in children is a distinct node from no node — and autofixes should never introduce semantic changes.

This fix adds a guard in shouldCheckForUnnecessaryCurly to skip empty string literals when their parent is a JSX element (children context). The behavior for props is unchanged: bar={""} is still flagged and correctly auto-fixed to bar="", since both forms pass an identical empty string to the prop.

Fixes #3995

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.58%. Comparing base (9af8845) to head (fbec3ee).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3996      +/-   ##
==========================================
+ Coverage   94.76%   97.58%   +2.81%     
==========================================
  Files         134      137       +3     
  Lines       10165    10183      +18     
  Branches     3794     3799       +5     
==========================================
+ Hits         9633     9937     +304     
+ Misses        532      246     -286     

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