[DOC] Remove deprecated `account_id` field from `mws_credentials` resource

[frosforever]

Affected Resource(s)

mws_credentials https://registry.terraform.io/providers/databricks/databricks/latest/docs/resources/mws_credentials

List of things to potentially add/remove:

This is a list of things to manipulate in the docs:

• [ ] account_id is deprecated and should be labeled as such.
• [ ] Example usage reference account_id should be updated

Important Factoids

Using account_id can lead to issues like #3016 & #3059

References

https://github.com/databricks/terraform-provider-databricks/commit/3c89aee8d7d457407473d89cd0ce0ef46f703ea2#diff-d31a73b687cffca05e7023c32777485f2ebde6261bec07296c05a75de39898afR114 #3028