deprecated Trainer proc_rank

[Borda]

What does this PR do?

Fixes #2267

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[codecov]

Codecov Report

Merging #2269 into master will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #2269   +/-   ##
======================================
  Coverage      88%     88%           
======================================
  Files          70      70           
  Lines        5486    5491    +5     
======================================
+ Hits         4814    4819    +5     
  Misses        672     672