[v25.2.x] iceberg: fix lint

[andrwng]

Follow-up to an auto-merged PR:
#27520

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.2.x
• v25.1.x
• v24.3.x

Release Notes

• none

[dotnwat]

fix for lint

[vbotbuildovich]

CI test results

test results on build#72043

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason
RandomNodeOperationsTest	test_node_operations	{"cloud_storage_type": 2, "compaction_mode": "adjacent_merge", "enable_failures": true, "mixed_versions": true, "with_iceberg": false}	integration	https://buildkite.com/redpanda/redpanda/builds/72043#0199366c-74b6-4637-ac2a-85b7a6f3042f	FLAKY	20/21	upstream reliability is '100.0'. current run reliability is '95.23809523809523'. drift is 4.7619 and the allowed drift is set to 50. The test should PASS
TopicDeleteCloudStorageTest	drop_lifecycle_marker_test	{"cloud_storage_type": 2}	integration	https://buildkite.com/redpanda/redpanda/builds/72043#0199366e-d5f7-4ba5-85c1-b232c4ad84e2	FLAKY	18/21	upstream reliability is '100.0'. current run reliability is '85.71428571428571'. drift is 14.28571 and the allowed drift is set to 50. The test should PASS