[CI] MappingStatsTests testToXContent failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #11453 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11449 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11445 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11441 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11437 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11429 / rhel-10_platform-support-unix
• elasticsearch-periodic-platform-support #11425 / rhel-10_platform-support-unix

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.action.admin.cluster.stats.MappingStatsTests.testToXContent" -Dtests.seed=D124DB79D81DA821 -Dtests.locale=lo-Laoo-LA -Dtests.timezone=Australia/Melbourne -Druntime.java=25

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.junit.ComparisonFailure: expected:<..._mapping_size" : "25[5b",
    "total_deduplicated_mapping_size_in_bytes" : 255],
    "field_types" ...> but was:<..._mapping_size" : "25[9b",
    "total_deduplicated_mapping_size_in_bytes" : 259],
    "field_types" ...>

Issue Reasons:

• [main] 7 consecutive failures in step rhel-10_platform-support-unix
• [main] 7 failures in test testToXContent (0.7% fail rate in 974 executions)
• [main] 7 failures in step rhel-10_platform-support-unix (100.0% fail rate in 7 executions)
• [main] 7 failures in pipeline elasticsearch-periodic-platform-support (100.0% fail rate in 7 executions)

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

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)