Update timeout error message in AutoMLExperiment.cs

[LittleLittleCloud]

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fix dotnet/machinelearning-modelbuilder#2500

[luisquintanilla]

@LittleLittleCloud looks good. Just made some minor suggestions.

[codecov]

Codecov Report

Merging #6613 (0d4c786) into main (6002aa8) will increase coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6613      +/-   ##
==========================================
+ Coverage   68.39%   68.44%   +0.04%     
==========================================
  Files        1176     1176              
  Lines      248210   248210              
  Branches    25915    25915              
==========================================
+ Hits       169759   169882     +123     
+ Misses      71676    71567     -109     
+ Partials     6775     6761      -14     

Flag	Coverage Δ
Debug	68.44% <ø> (+0.04%)	⬆️
production	62.83% <ø> (+0.06%)	⬆️
test	88.86% <ø> (-0.01%)	⬇️

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see 9 files with indirect coverage changes