fix: improve UserWarning message

[Lucklyric]

improve UserWarning message when both overfit and training dataloader shuffling are enabled

What does this PR do?

Fixes #7656

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[codecov]

Codecov Report

Merging #7685 (5a7f347) into master (ad168fc) will decrease coverage by 5%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #7685    +/-   ##
=======================================
- Coverage      93%     88%    -5%     
=======================================
  Files         199     199            
  Lines       12957   12957            
=======================================
- Hits        11988   11368   -620     
- Misses        969    1589   +620