fix: add __init__.py to data_layer module

[UsamaSadiq]

Description

• Previous release 5.2.2 failed when bumping the version in edx-platform in the PR due to insufficient files being published in the PyPI release.
• Added __init__.py to xblock/data_layer module to fix the issue.
• Bump the package version to 5.2.3 after the docs failure has been fixed.
• If this release works successfully, the previous release 5.2.2 will need to be yanked from PyPI.
• downgrade pylint to avoid quality failures

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.01% ⚠️

Comparison is base (0faef57) 95.08% compared to head (ca4b643) 95.08%.

❗ Current head ca4b643 differs from pull request most recent head bac9dd8. Consider uploading reports for the commit bac9dd8 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2020      +/-   ##
==========================================
- Coverage   95.08%   95.08%   -0.01%     
==========================================
  Files         158      158              
  Lines       17429    17428       -1     
  Branches     1626     1625       -1     
==========================================
- Hits        16572    16571       -1     
  Misses        642      642              
  Partials      215      215              

Flag	Coverage Δ
unittests	95.08% <100.00%> (-0.01%)	⬇️

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Files Changed	Coverage Δ
openassessment/__init__.py	100.00% <100.00%> (ø)
openassessment/xblock/data_layer/serializers.py	95.76% <100.00%> (ø)
...enassessment/xblock/data_layer/test_serializers.py	100.00% <100.00%> (ø)

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[awais786]

#2022