fix: bug in resolve_lines

[charlesmindee]

This PR fixes a bug in resolve_lines, which was not updating the y_center of the lines thus each box of the document was assigned to a new line.
Any feedback is welcome!

[fg-mindee]

Would you mind merging main to fix the PyTorch test please? 🙏

[fg-mindee]

Thanks for catching this!

Perhaps we should create a unittest for a basic word to line aggregation?

[codecov]

Codecov Report

Merging #537 (bff22c9) into main (323d484) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #537      +/-   ##
==========================================
- Coverage   95.38%   95.36%   -0.03%     
==========================================
  Files         109      109              
  Lines        4182     4182              
==========================================
- Hits         3989     3988       -1     
- Misses        193      194       +1     

Flag	Coverage Δ
unittests	95.36% <100.00%> (-0.03%)	⬇️

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Impacted Files	Coverage Δ
doctr/models/builder.py	92.70% <100.00%> (ø)
...dels/detection/differentiable_binarization/base.py	91.19% <0.00%> (-0.63%)	⬇️

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[charlesmindee]

This is how it looks like now: