Prepare release 2.15.1

[opensearch-trigger-bot]

Automated Release Preparation

This PR prepares the release branch for version 2.15.1.

Automated Changes

• Updated gradle.properties version to 2.15.1
• Generated THIRD-PARTY file

Manual Steps Remaining

Before merging this PR:

• Review the version number is correct
• Review the THIRD-PARTY file changes

After merging this PR:

• Prepare release notes (see release notes script)
• Run the Release Artifacts workflow
• Approve the release issue (requires 2 maintainer approvals)
• Update the draft release with release notes
• Publish the release
• Close the milestone

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Branch: 2.15

Generated by the Prepare Patch Release workflow

[github-actions]

Unit Test Results

  3 141 files  ±0    3 141 suites  ±0   1h 34m 15s ⏱️ + 2m 23s
13 492 tests  - 3  13 484 ✔️  - 3    7 💤 ±0  1 ❌ ±0 
30 253 runs  ±0  30 237 ✔️ ±0  15 💤 ±0  1 ❌ ±0 

For more details on these failures, see this check.

Results for commit 59c846e. ± Comparison against base commit 39e5d68.

♻️ This comment has been updated with latest results.