IMPALA-6677: [DOCS] Document the next_day function
IMPALA-6677: [DOCS] Document the next_day function

Change-Id: I2dacc86ff69a1016b1863d9db66dd29fd832b715
Reviewed-on: http://gerrit.cloudera.org:8080/10893
Reviewed-by: Vuk Ercegovac <5107d507b3ff60bf5aa22409fbf08a8c84cb58d8@cloudera.com>
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>

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