[CI] DedicatedClusterSnapshotRestoreIT testRestoreShrinkIndex failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #6588 / windows-2022_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #6567 / windows-2019_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #6553 / windows-2022_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #6532 / windows-2022_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #6518 / windows-2019_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #6441 / windows-2022_checkpart1_platform-support-windows

Reproduction Line:

gradlew ":server:internalClusterTest" --tests "org.elasticsearch.snapshots.DedicatedClusterSnapshotRestoreIT.testRestoreShrinkIndex" -Dtests.seed=F6FDAA05ED542B2A -Dtests.locale=os -Dtests.timezone=Pacific/Auckland -Druntime.java=23

Applicable branches:
8.x

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.IllegalStateException: Some shards are still open after the threadpool terminated. Something is leaking index readers or store references.

Issue Reasons:

• [8.x] 6 failures in test testRestoreShrinkIndex (0.7% fail rate in 862 executions)
• [8.x] 4 failures in step windows-2022_checkpart1_platform-support-windows (22.2% fail rate in 18 executions)
• [8.x] 2 failures in step windows-2019_checkpart1_platform-support-windows (12.5% fail rate in 16 executions)
• [8.x] 6 failures in pipeline elasticsearch-periodic-platform-support (27.3% fail rate in 22 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticsearchmachine]

Pinging @elastic/es-distributed-coordination (Team:Distributed Coordination)