[Backport 2.19] update put route when flattening result index

[opensearch-trigger-bot]

Backport d4ce6cf from #1409.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 81.63%. Comparing base (328f901) to head (1947887).
Report is 1 commits behind head on 2.19.

Files with missing lines	Patch %	Lines
.../rest/handler/AbstractTimeSeriesActionHandler.java	80.00%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               2.19    #1411      +/-   ##
============================================
- Coverage     81.69%   81.63%   -0.07%     
+ Complexity     5879     5870       -9     
============================================
  Files           533      533              
  Lines         23676    23665      -11     
  Branches       2375     2374       -1     
============================================
- Hits          19343    19319      -24     
- Misses         3178     3186       +8     
- Partials       1155     1160       +5     

Flag	Coverage Δ
plugin	81.63% <80.00%> (-0.07%)	⬇️

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

Files with missing lines	Coverage Δ
...g/opensearch/timeseries/util/RestHandlerUtils.java	67.46% <ø> (+3.64%)	⬆️
.../rest/handler/AbstractTimeSeriesActionHandler.java	93.07% <80.00%> (-0.20%)	⬇️

... and 10 files with indirect coverage changes