Revert changes to tasks_list test rest api spec test

[jed326]

Description

DIscovered a problem with one of the test updates in #7673 as a part of the backport #7856.
resource_stats does not exist in OS < 2.X so I am reverting the update to the test.

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)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.backpressure.SearchBackpressureIT.testSearchShardTaskCancellationWithHighCpu
      1 org.opensearch.remotestore.RemoteStoreRefreshListenerIT.testRemoteRefreshRetryOnFailure
      1 org.opensearch.indices.replication.SegmentReplicationRelocationIT.testPrimaryRelocation

• URL: https://build.ci.opensearch.org/job/gradle-check/16689/
• CommitID: 16fdfff
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[andrross]

Can you pull the resource_stats test into its own case with the version skip to prevent it from running on versions below 2.x?

[codecov]

Codecov Report

Merging #7875 (c13c956) into main (57c4a80) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #7875      +/-   ##
============================================
- Coverage     70.88%   70.88%   -0.01%     
- Complexity    56272    56293      +21     
============================================
  Files          4687     4687              
  Lines        266232   266232              
  Branches      39095    39095              
============================================
- Hits         188714   188711       -3     
- Misses        61519    61523       +4     
+ Partials      15999    15998       -1     

see 467 files with indirect coverage changes

[jed326]

resource_stats is not present on 2.0 -- https://github.com/opensearch-project/OpenSearch/blob/2.0/server/src/main/java/org/opensearch/tasks/Task.java

Moved it into it's own test case that skips below 2.1

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/16700/
• CommitID: c13c956

[reta]

@jed326 I don't think we need to revert the changes, we just need to add version condition, I will push the change here #7856

[jed326]

Closing this PR then since it's merged in #7889