Update build.gradle snapshot to 2.9.1

[monusingh-1]

Increment version to 2.9.1

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]

Codecov Report

Merging #1182 (9ad31e6) into 2.9 (bba2de6) will decrease coverage by 1.81%.
The diff coverage is n/a.

❗ Current head 9ad31e6 differs from pull request most recent head 554ad80. Consider uploading reports for the commit 554ad80 to get more accurate results

@@             Coverage Diff              @@
##                2.9    #1182      +/-   ##
============================================
- Coverage     76.79%   74.99%   -1.81%     
+ Complexity     1060     1042      -18     
============================================
  Files           141      141              
  Lines          4771     4771              
  Branches        546      546              
============================================
- Hits           3664     3578      -86     
- Misses          756      850      +94     
+ Partials        351      343       -8     

see 21 files with indirect coverage changes

[monusingh-1]

 Can't get https://ci.opensearch.org/ci/dbc/distribution-build-opensearch/2.9.1/latest/linux/x64/tar/builds/opensearch/plugins/opensearch-security-2.9.1.0.zip to /home/runner/work/cross-cluster-replication/cross-cluster-replication/build/dependencies/security/opensearch-security-2.9.1.0.zip

Security plugin 2.9.1 not available yet