Fix failing bwc tests

[sruti1312]

Signed-off-by: Sruti Parthiban partsrut@amazon.com

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Fix failing bwc tests

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• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
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[sruti1312]

This PR fixes the 2.1 artifact link used in bwc tests. But the BWC tests are still failing with the following error. From error logs, looks like the tests are failing because of cluster formation issues. Possibly related to #190

> Task :paBwcCluster#mixedClusterTask FAILED
FAILURE: Build failed with an exception.

* Where:
Build file '/home/runner/work/performance-analyzer/performance-analyzer/tmp/performance-analyzer/build.gradle' line: [649](https://github.com/opensearch-project/performance-analyzer/actions/runs/3129730314/jobs/5079172903#step:11:650)

* What went wrong:
Execution failed for task ':paBwcCluster#mixedClusterTask'.
> `cluster{::paBwcCluster0}` failed to wait for cluster health yellow after 40 SECONDS
    IO error while waiting cluster
    503 Service Unavailable