[KGA-64] dev: remove dead code in exec_create

[enitrat]

https://github.com/code-423n4/2024-09-kakarot-findings/issues/70

Removes a portion of dead code that cheks the return value of the add_transfer function in exec_create. Because the case where the sender doesn't have enough balance is manually handled before, this branch can not be executed.

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This change is 

[notion-workspace]

In exec_create, if unable to transfer value, evm should be returned, not child_evm #70

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 63.7%. Comparing base (0fbea3a) to head (64f522f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
..._zero/kakarot/instructions/system_operations.cairo	0.0%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1611   +/-   ##
=====================================
  Coverage   63.7%   63.7%           
=====================================
  Files         44      44           
  Lines       8362    8359    -3     
=====================================
  Hits        5332    5332           
+ Misses      3030    3027    -3     

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