Fix incorrect chapter numbers returned from usfm_structure_extractor

[pmachapman]

Fixes #308

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This change is 

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.70%. Comparing base (828bb4d) to head (57f7230).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #315      +/-   ##
==========================================
+ Coverage   90.39%   91.70%   +1.31%     
==========================================
  Files         355      359       +4     
  Lines       22843    23473     +630     
==========================================
+ Hits        20648    21525     +877     
+ Misses       2195     1948     -247     

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[Enkidu93]

I understand better how we missed this. I was puzzled how we could have had a bug that wasn't caught when this is so well-tested. Thanks for doing this, Peter!

@Enkidu93 reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on ddaspit).

[mshannon-sil]

Thanks Peter! I confirmed that fixes it where it's needed in SILNLP as well.

@mshannon-sil reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on ddaspit).