Bump to OpenSearch 2.6

[lezzago]

Description

Bump to OpenSearch 2.6

Issues Resolved

N/A

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov-commenter]

Codecov Report

Merging #351 (ef8de0d) into 2.x (3444c39) will decrease coverage by 0.02%.
The diff coverage is 13.33%.

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@@             Coverage Diff              @@
##                2.x     #351      +/-   ##
============================================
- Coverage     36.51%   36.49%   -0.02%     
+ Complexity      886      885       -1     
============================================
  Files           185      185              
  Lines          7098     7110      +12     
  Branches        860      860              
============================================
+ Hits           2592     2595       +3     
- Misses         4268     4278      +10     
+ Partials        238      237       -1     

Impacted Files	Coverage Δ
...urityanalytics/action/GetMappingsViewResponse.java	0.00% <0.00%> (ø)
...ytics/transport/TransportDeleteDetectorAction.java	0.00% <ø> (ø)
...lytics/transport/TransportIndexDetectorAction.java	0.00% <ø> (ø)
...rityanalytics/action/GetIndexMappingsResponse.java	35.00% <20.00%> (-0.72%)	⬇️
...ecurityanalytics/action/ValidateRulesResponse.java	48.57% <20.00%> (-3.05%)	⬇️
...g/opensearch/securityanalytics/model/Detector.java	70.58% <0.00%> (+0.34%)	⬆️

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