[Fix] fix num_classes in lvis config files

[hellock]

Fix #3593

[codecov]

Codecov Report

Merging #3627 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3627   +/-   ##
=======================================
  Coverage   60.85%   60.85%           
=======================================
  Files         205      205           
  Lines       13809    13809           
  Branches     2341     2341           
=======================================
  Hits         8403     8403           
  Misses       4977     4977           
  Partials      429      429           

Flag	Coverage Δ
#unittests	60.85% <ø> (ø)

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[hellock]

@ZwwWayne Pretrained models need to be updated.