Fix error when budgets_to_optimize are specified

[ricardoV94]

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📚 Documentation preview 📚: https://pymc-marketing--1440.org.readthedocs.build/en/1440/

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.54%. Comparing base (e4a2664) to head (83b3ac1).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
pymc_marketing/mmm/budget_optimizer.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1440      +/-   ##
==========================================
- Coverage   94.55%   94.54%   -0.02%     
==========================================
  Files          50       50              
  Lines        5422     5423       +1     
==========================================
  Hits         5127     5127              
- Misses        295      296       +1     

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[cetagostini]

Solving bug on #1439

Modifying to pass test.

[ricardoV94]

I like kwarg only arguments :(

[wd60622]

Closes #1439