[v25.1.x] deps: update libxml2 from 2.14.5 to 2.14.6

[tyson-redpanda]

Backport of PR #29423

FIXES=CORE-15341

[vbotbuildovich]

CI test results

test results on build#79777

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason	test_history
RestCatalogConnectionTest	test_redpanda_connection_to_rest_catalog	{"cloud_storage_type": 1}	integration	https://buildkite.com/redpanda/redpanda/builds/79777#019c053c-b620-4686-8310-672869aa9d9e	FLAKY	18/21	Test PASSES after retries.No significant increase in flaky rate(baseline=0.0667, p0=0.3889, reject_threshold=0.0100. adj_baseline=0.1870, p1=0.2492, trust_threshold=0.5000)	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=RestCatalogConnectionTest&test_method=test_redpanda_connection_to_rest_catalog

[vbotbuildovich]

Retry command for Build#79777

please wait until all jobs are finished before running the slash command

/ci-repeat 1
skip-redpanda-build
skip-units
skip-rebase
tests/rptest/tests/delete_records_test.py::DeleteRecordsTest.test_delete_records_concurrent_truncations@{"cloud_storage_enabled":true,"truncate_point":"random_offset"}