Fix misleading file extension for partition statistics #8824

Job	Run time
integration-test-gcs	1m 22s
integration-test-adls	1m 24s
cibw-dev-env-smoke-test	24s
integration-test-s3	1m 21s
integration-test	11m 0s
lint-and-unit-test (3.12)	3m 18s
lint-and-unit-test (3.10)	3m 5s
lint-and-unit-test (3.14)	2m 40s
lint-and-unit-test (3.13)	3m 2s
lint-and-unit-test (3.11)	3m 11s
integration-coverage-report	28s
	31m 15s

Provide feedback