Use upload_files_v2 Slack SDK method by default in Slack Operators

[Taragolis]

Couple days ago Slack sent auto message to my my email which informed me that files.upload discontinued soon

Hello Andrey Anshin,

A workspace that you administer contains apps or integrations that recently used the files.upload web API method. We want to inform you about two important changes coming to support for the files.upload API.

May 8, 2024
Newly created Slack apps will no longer be able to access the files.upload API. Existing applications will be able to continue using files.upload until support is discontinued.

March 11, 2025
Support for the files.upload API for all apps will be discontinued.

Link for more details about upcoming changes: https://api.slack.com/changelog/2024-04-a-better-way-to-upload-files-is-here-to-stay

Recently we add support of v2 method #36757, and also add SlackHook.send_file_v1_to_v2 for smooth transition between v1 and v2 which used in operators under the hood

So I would propose to switch by default to v2:

• Users who create Slack Apps after the May 8, 2024 has not affected and could use Slack Operators which intends to send files into the slack
• Users who use Slack Apps which created before May 8, 2024 should grant additional scopes for the application, no mandatory changes required in existed tasks

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[amoghrajesh]

Late to the party, looks good +1