[Backport 2.x] Bump apache-rat from 0.13 to 0.15

[Rishikesh1159]

Signed-off-by: Rishikesh1159 rishireddy1159@gmail.com

Description

This PR backports #5675

Issues Resolved

[List any issues this PR will resolve]

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
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/8752/
• CommitID: 3193314

[codecov-commenter]

Codecov Report

Merging #5686 (3193314) into 2.x (934600f) will increase coverage by 0.03%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #5686      +/-   ##
============================================
+ Coverage     70.57%   70.61%   +0.03%     
- Complexity    58615    58636      +21     
============================================
  Files          4740     4740              
  Lines        280522   280522              
  Branches      40883    40883              
============================================
+ Hits         197982   198086     +104     
+ Misses        66113    66001     -112     
- Partials      16427    16435       +8     

Impacted Files	Coverage Δ
...g/opensearch/index/analysis/CharFilterFactory.java	0.00% <0.00%> (-100.00%)	⬇️
...port/ResponseHandlerFailureTransportException.java	0.00% <0.00%> (-60.00%)	⬇️
.../java/org/opensearch/search/dfs/AggregatedDfs.java	54.83% <0.00%> (-41.94%)	⬇️
...ava/org/opensearch/search/dfs/DfsSearchResult.java	43.26% <0.00%> (-35.58%)	⬇️
...min/cluster/snapshots/get/GetSnapshotsRequest.java	52.63% <0.00%> (-31.58%)	⬇️
...rc/main/java/org/opensearch/ingest/IngestInfo.java	51.72% <0.00%> (-27.59%)	⬇️
.../java/org/opensearch/index/reindex/RemoteInfo.java	51.37% <0.00%> (-22.94%)	⬇️
...a/org/opensearch/transport/netty4/Netty4Utils.java	42.42% <0.00%> (-21.22%)	⬇️
...tions/bucket/terms/ParsedSignificantLongTerms.java	73.68% <0.00%> (-21.06%)	⬇️
...main/java/org/opensearch/ingest/ProcessorInfo.java	47.36% <0.00%> (-21.06%)	⬇️
... and 481 more

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