Fix PTL import

[AleksanderWWW]

Before submitting checklist

• Did you update the CHANGELOG? (not for test updates, internal changes/refactors or CI/CD setup)
• Did you ask the docs owner to review all the user-facing changes?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 75.04%. Comparing base (fd03119) to head (843fd14).

Files	Patch %	Lines
...neptune/integrations/pytorch_lightning/__init__.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           dev/1.x    #1719   +/-   ##
========================================
  Coverage    75.04%   75.04%           
========================================
  Files          304      304           
  Lines        15050    15050           
========================================
+ Hits         11294    11295    +1     
+ Misses        3756     3755    -1     

Flag	Coverage Δ
macos	74.71% <0.00%> (ø)
py3.7	75.04% <0.00%> (+<0.01%)	⬆️
ubuntu	74.91% <0.00%> (+0.05%)	⬆️
unit	75.04% <0.00%> (+<0.01%)	⬆️
windows	73.96% <0.00%> (ø)

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