Removed Turnover Target Number Method Configuration

[IllianiCBT]

Deleted the turnover target number method and related difficulty settings. Simplified turnover check logic to always use fixed target numbers directly without HR skill adjustments or difficulty modifiers.

Unfortunately, the Negotiation and Administration-tied turnover target number methods were resulting in a very poor play experience. This issue was fundamental and beyond my ability to resolve, so I opted to move to effectively only include the 'fixed' method as this provides the most balanced experience for all players, while still being easy to configure.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 10.32%. Comparing base (0ecc4a0) to head (90fc1b4).
Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #4509      +/-   ##
============================================
- Coverage     10.33%   10.32%   -0.01%     
+ Complexity     5824     5812      -12     
============================================
  Files           935      934       -1     
  Lines        128395   128272     -123     
  Branches      18889    18867      -22     
============================================
- Hits          13270    13249      -21     
+ Misses       113849   113747     -102     
  Partials       1276     1276              

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