Remove deprecated S3ToSnowflake and SnowflakeToSlack operators

[Taragolis]

During #33557 found that SnowflakeToSlackOperator is a deprecated version of SqlToSlackOperator

In additional I would like to remove S3ToSnowflakeOperator which is deprecated version of more generic CopyFromExternalStageToSnowflakeOperator

Maybe it is also a good idea to remove SnowflakeOperator, which is also deprecated

ToDo:

• Update documentation if required
• Add breaking changes

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[potiuk]

LGTM

[eladkal]

I wonder if we should somehow find a way to indicate that this capability is still available via other provider (in automated manner)

My thought here is that users who need this capability might not look at Slack docs. I think it can be very nice if we can indicate in the provider about all the capabilities that can be used with this service regardless if their code base is part of this provider or not (simply mention it existed and reference to the right package but in an automated way)