Clarify statement_count behavior in SnowflakeSqlApi docstrings

[justinpakzad]

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Tiny change to SnowflakeSqlApiHook & SnowflakeSqlApiOperator docstrings to inform users that they can set statement_count = 0 if they want to submit a variable number of SQL statements without specifying the exact count.

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[justinpakzad]

Failure seems to be an issue with preparing breeze/CI image. Needs a re-run.