Make non-standard default for Snowflake rank-related functions' window frame explicit

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Coverage tests results

401 tests  ±0   194 :white_check_mark: ±0   4s :stopwatch: ±0s   2 suites ±0     0 :zzz: ±0    2 files   ±0   207 :x: ±0 

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Results for commit 17ce7582. ± Comparison against base commit bd18476f.

:recycle: This comment has been updated with latest results.