Fix broken trainer flags nb

[nateraw]

What does this PR do?

Fixes issue where notebook json was corrupted somehow. uploaded via colab this time, hopefully it works.

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[codecov]

Codecov Report

Merging #4159 into master will decrease coverage by 5%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #4159    +/-   ##
=======================================
- Coverage      93%     88%    -5%     
=======================================
  Files         103     103            
  Lines        7798    8360   +562     
=======================================
+ Hits         7232    7364   +132     
- Misses        566     996   +430