DOC Remove warning from sklearn example.

[MuawizChaudhary]

Dear Esteemed Colleagues,

please accept my State of the Art (SOTA) result on the "Kymatio Sklearn Digit Recognition Benchmark" Benchmark.

Love,
ScatteringSepoy

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To be much less trolly, this PR removes a warning thrown by sklearn about a lack of convergence, while keeping the same runtime and improving accuracy by about 1.5 percent.

This goes a small way of solving #817 .

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.03%. Comparing base (ca9073f) to head (d851c67).
Report is 40 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #828   +/-   ##
=======================================
  Coverage   88.03%   88.03%           
=======================================
  Files          64       64           
  Lines        2323     2323           
=======================================
  Hits         2045     2045           
  Misses        278      278           

Flag	Coverage Δ
jenkins_main	88.03% <ø> (ø)

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