Fix failing doctests

[drbenvincent]

• Closes Fix failing doctests #323 which is affecting current PR's.
• Also managed to catch a bug where we were not passing in random_seed to pm.sample_posterior_predictive in ModelBuilder.predict. Also replaced a multi-line block with the single line random_seed = self.sample_kwargs.get("random_seed", None) which is much nicer.
• Other than that, the solution was to add varying numbers of <BLANKLINE> to the docstrings. I believe this is because the pymc progress bar is returning empty lines, possibly only in the instance where progressbar=False. I should open an issue in the PyMC repo about that.
• All tests and doctests pass in my local environment, which was build in the conda-based approach, see Move to a conda only install of pymc (local dev workflow) #304. Remains to be seen if the doctests will pass remotely.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.27%. Comparing base (dbaa17b) to head (8805fb2).
Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #330      +/-   ##
==========================================
+ Coverage   77.10%   77.27%   +0.17%     
==========================================
  Files          21       21              
  Lines        1380     1395      +15     
==========================================
+ Hits         1064     1078      +14     
- Misses        316      317       +1     

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[drbenvincent]

Hurray! Remote tests pass 🎉