Removing API docs from PDF

[john-science]

What is the change? Why is it being made?

Removing API docs from PDF, as they are not easy to read in PDF format, and make the ARMI docs over 1,600 pages long in PDF.

close #2288

SCR Information

Change Type: docs

One-Sentence Description: Removing API docs from PDF

One-line Impact on Requirements: NA

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.
• The documentation is still up-to-date in the doc folder.
• The code style follows good practices.
• The dependencies are still up-to-date in pyproject.toml.

[john-science]

Okay, this is proving somewhat harder than anticipated. The turn-around time on testing through github is just too long.