Doc: Update output of expire_snapshots procedure

[lvyanquan]

#4629 is already merged, but the the document hasn't been updated.
The execution output is inconsistent with the documentation, which will lead to confuse, this pr will fix it.

CALL spark_catalog.system.expire_snapshots('test_table');
0       0       0       0       1
Time taken: 7.254 seconds, Fetched 1 row(s)
22/09/27 17:32:43 INFO SparkSQLCLIDriver: Time taken: 7.254 seconds, Fetched 1 row(s)

[szehon-ho]

Thanks @lvyanquan , and @ajantha-bhat for review!