[Segment Replication] Remove deprecated feature flag check preventing SegmentReplicationSnapshotIT tests run

[dreamer-89]

Description

Remove feature flag check from SegmentReplicationSnapshotIT tests run which prevents these tests run under gradle check. This was missed in #5941 while backporting #4959 into 2.x

Issues Related

#6761

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: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/12831/
• CommitID: 6f3e86a
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=pit/10_basic/Delete all}

• URL: https://build.ci.opensearch.org/job/gradle-check/12836/
• CommitID: 91bf08c
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.