Minor cleanup.

[eerhardt]

• Remove dead code in PredictionEngine.cs
• Fix build warnings

[codecov]

Codecov Report

Merging #5770 (f4e4081) into main (d8fe817) will increase coverage by 20.81%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main    #5770       +/-   ##
===========================================
+ Coverage   68.38%   89.20%   +20.81%     
===========================================
  Files        1131      231      -900     
  Lines      241019    49268   -191751     
  Branches    25024     2044    -22980     
===========================================
- Hits       164826    43950   -120876     
+ Misses      69707     4949    -64758     
+ Partials     6486      369     -6117     

Flag	Coverage Δ
Debug	89.20% <ø> (+20.81%)	⬆️
production	?
test	89.20% <ø> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
test/Microsoft.ML.AutoML.Tests/AutoFitTests.cs	87.07% <0.00%> (-1.97%)	⬇️
...ransformInference/TransformPostTrainerInference.cs
src/Microsoft.ML.Data/Data/Conversion.cs
src/Microsoft.ML.FastTree/FastTreeRanking.cs
src/Microsoft.ML.EntryPoints/ImportTextData.cs
src/Microsoft.ML.FastTree/Training/ScoreTracker.cs
src/Microsoft.ML.Data/Transforms/NopTransform.cs
src/Microsoft.ML.Sweeper/Parameters.cs
...rc/Microsoft.ML.Ensemble/OutputCombiners/Median.cs
.../Evaluators/Metrics/BinaryClassificationMetrics.cs
... and 889 more

[michaelgsharp]

[eerhardt]

I rebased on the latest in hopes that CI will pass now.