azurerm_logic_app_standard - Add new computed attribute auto_swap_slot_name

[magodo]

This attribute exists in the code (Read function), but is not defined in the schema. This PR complements the schema and document. Otherwise, Read will fail with following error:

  | 2023/07/14 16:54:09 Invalid address to set: []string{"site_config", "0", "auto_swap_slot_name"}:

[github-actions]

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