fix: Fixed framework alignment on MobileNet V3 implementations

[fg-mindee]

This PR introduces the following modifications:

• fixed the implementation of mobilenetV3 versions
• passes the input shape for a proper model build in the unittests of backbones

Any feedback is welcome!

[charlesmindee]

Thanks!

[codecov]

Codecov Report

Merging #410 (466d748) into main (26f2167) will decrease coverage by 0.05%.
The diff coverage is 96.00%.

@@            Coverage Diff             @@
##             main     #410      +/-   ##
==========================================
- Coverage   95.88%   95.83%   -0.06%     
==========================================
  Files          91       91              
  Lines        3795     3838      +43     
==========================================
+ Hits         3639     3678      +39     
- Misses        156      160       +4     

Flag	Coverage Δ
unittests	95.83% <96.00%> (-0.06%)	⬇️

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Impacted Files	Coverage Δ
...etection/differentiable_binarization/tensorflow.py	97.47% <ø> (ø)
doctr/models/backbones/mobilenet/tensorflow.py	97.43% <95.91%> (-0.75%)	⬇️
doctr/models/utils/tensorflow.py	100.00% <100.00%> (ø)
doctr/datasets/ocr.py	89.09% <0.00%> (-2.81%)	⬇️
doctr/datasets/datasets/base.py	95.55% <0.00%> (+0.20%)	⬆️

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