fix type of 'n_gram' from bool to int in TranslationTask

[BrightXiaoHan]

What does this PR do?

fix type of 'n_gram' from bool to int in TranslationTask

Fixes #1485

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[codecov]

Codecov Report

Base: 92.34% // Head: 83.24% // Decreases project coverage by -9.10% ⚠️

Coverage data is based on head (a0e21a8) compared to base (0e1a9fe).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1486      +/-   ##
==========================================
- Coverage   92.34%   83.24%   -9.11%     
==========================================
  Files         292      292              
  Lines       13158    13158              
==========================================
- Hits        12151    10953    -1198     
- Misses       1007     2205    +1198     

Flag	Coverage Δ
pytest	13.03% <ø> (ø)
tpu	13.03% <ø> (ø)
unittests	83.72% <ø> (-9.16%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
flash/text/seq2seq/translation/model.py	95.45% <ø> (ø)
...lash/image/embedding/vissl/transforms/utilities.py	15.15% <0.00%> (-84.85%)	⬇️
flash/core/integrations/labelstudio/visualizer.py	24.00% <0.00%> (-72.00%)	⬇️
flash/image/embedding/heads/vissl_heads.py	35.29% <0.00%> (-64.71%)	⬇️
.../image/classification/integrations/baal/dropout.py	28.00% <0.00%> (-64.00%)	⬇️
flash/image/embedding/losses/vissl_losses.py	37.50% <0.00%> (-62.50%)	⬇️
flash/image/embedding/vissl/adapter.py	31.63% <0.00%> (-62.25%)	⬇️
flash/image/detection/input.py	38.88% <0.00%> (-61.12%)	⬇️
...ash/image/classification/integrations/baal/loop.py	33.82% <0.00%> (-59.56%)	⬇️
...age/face_detection/backbones/fastface_backbones.py	42.10% <0.00%> (-57.90%)	⬇️
... and 63 more

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[ethanwharris]

Thanks! LGTM 😃