[FEAT] Update product_class str method

[samar-hassan]

No description provided.

[codecov]

Codecov Report

Merging #4248 (604a0ce) into master (cb93f5e) will not change coverage.
Report is 2 commits behind head on master.
The diff coverage is 100.00%.

❗ Current head 604a0ce differs from pull request most recent head 89efd48. Consider uploading reports for the commit 89efd48 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4248   +/-   ##
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  Coverage   87.84%   87.84%           
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  Files         291      291           
  Lines       16145    16145           
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  Hits        14182    14182           
  Misses       1963     1963           

Files	Coverage Δ
src/oscar/apps/catalogue/abstract_models.py	93.11% <100.00%> (ø)