Fix repr error when CLVModel is not yet built

[ricardoV94]

Description

The reason for separating model definition and model building in ModelBuilder is still elusive to me (cc @twiecki), but anyway this fixes the assumption that used to be true for CLVModels prior to them inheriting ModelBuilder

Related Issue

• Closes CLV models don't have working repr without model fit #559
• Closes .build_model() Inconsistencies #318

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Modules affected

• MMM
• CLV

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

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📚 Documentation preview 📚: https://pymc-marketing--563.org.readthedocs.build/en/563/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.37%. Comparing base (608a446) to head (f8b18aa).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #563   +/-   ##
=======================================
  Coverage   91.36%   91.37%           
=======================================
  Files          21       21           
  Lines        2073     2075    +2     
=======================================
+ Hits         1894     1896    +2     
  Misses        179      179           

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[ColtAllen]

This is a simple fix and seems like a prerequisite to #564 which is a big one, so let's get this one merged.