Update public documentation regarding deprecation of operators

[pankajkoti]

Highlight 1.19 related notes in public documentation for astronomer-providers.
It's essential for us to closely coordinate with the documentation and CRE teams
throughout the release to ensure seamless communication. In our GitHub repo docs,
we should suggest using Async operators from OSS repo instead of using ours.

[vatsrahul1001]

With the SnowflakeSqlApiHookAsync, we neglected to specify the region while constructing the URL. In the connection, we were appending the region to the account name only. However, in the OSS hook, the URL is constructed using the region. Therefore, we can now update the region field in the connection and remove the region from the account field.

[pankajkoti]

Created draft PR: #1468