[CI] SearchableSnapshotsPrewarmingIntegTests.testConcurrentPrewarming fails on CI

[tlrx]

Build scan:
https://gradle-enterprise.elastic.co/s/7lytl32v5nhso
https://gradle-enterprise.elastic.co/s/7hdrmguklhuxq

Repro line:

Reproduces locally?:
No

Applicable branches:
master

Failure excerpt:

java.lang.AssertionError: Blob [__hBbReAqXTUGYJ6P1sR9ZTw.part7] not fully warmed
Expected: a value equal to or greater than <772L>
     but: <725L> was less than <772L>
	at __randomizedtesting.SeedInfo.seed([309FAA2B385BE603:78FC385D5105D25C]:0)
	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
	at org.junit.Assert.assertThat(Assert.java:956)
	at org.elasticsearch.xpack.searchablesnapshots.SearchableSnapshotsPrewarmingIntegTests.testConcurrentPrewarming(SearchableSnapshotsPrewarmingIntegTests.java:300)

[elasticmachine]

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