fix: Remove incorrect SSH key authentication claim from SFTP docs

The FTP/SFTP comparison table claimed SFTP supports "Username/password
or SSH keys" for authentication. The SFTP connector only defines
user and pass parameters — no SSH key file or passphrase parameters
exist. Changed to "Username/password" to match the implementation.

Author: claudespice

website/docs/components/data-connectors/ftp.md

@@ -34,7 +34,7 @@ SELECT * FROM sales LIMIT 10;
 | --------------- | ------------------------- | ------------------------------ |
 | Default Port    | 21                        | 22                             |
 | Encryption      | None (plain text)         | SSH encryption                 |
-| Authentication  | Username/password         | Username/password or SSH keys  |
+| Authentication  | Username/password         | Username/password              |
 | Recommended Use | Internal/trusted networks | Production and public networks |
 
 :::tip[Security Recommendation]

website/versioned_docs/version-1.11.x/components/data-connectors/ftp.md

@@ -34,7 +34,7 @@ SELECT * FROM sales LIMIT 10;
 | --------------- | ------------------------- | ------------------------------ |
 | Default Port    | 21                        | 22                             |
 | Encryption      | None (plain text)         | SSH encryption                 |
-| Authentication  | Username/password         | Username/password or SSH keys  |
+| Authentication  | Username/password         | Username/password              |
 | Recommended Use | Internal/trusted networks | Production and public networks |
 
 :::tip[Security Recommendation]