chore: follow udf error format for reduce

[yhl25]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@e3a0f30). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...java/io/numaproj/numaflow/accumulator/Service.java	50.00%	0 Missing and 1 partial ⚠️
...ain/java/io/numaproj/numaflow/reducer/Service.java	87.50%	0 Missing and 1 partial ⚠️
...a/io/numaproj/numaflow/reducestreamer/Service.java	88.88%	0 Missing and 1 partial ⚠️
...a/io/numaproj/numaflow/sessionreducer/Service.java	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #199   +/-   ##
=======================================
  Coverage        ?   59.05%           
  Complexity      ?      477           
=======================================
  Files           ?      151           
  Lines           ?     3417           
  Branches        ?      235           
=======================================
  Hits            ?     2018           
  Misses          ?     1229           
  Partials        ?      170           

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