Update README.md

[mrm8488]

• Show that the last uploaded version was trained on more data (custom_license files)

[codecov-io]

Codecov Report

Merging #3552 into master will decrease coverage by 0.49%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3552      +/-   ##
==========================================
- Coverage   78.31%   77.81%   -0.50%     
==========================================
  Files         100      100              
  Lines       17064    17064              
==========================================
- Hits        13363    13278      -85     
- Misses       3701     3786      +85     

Impacted Files	Coverage Δ
src/transformers/data/processors/squad.py	28.89% <0.00%> (-27.60%)	⬇️

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