Doc: add some missing description for ssl_mode and server_ca_mode. (#12006)

Author: feng-zhe

mmv1/third_party/terraform/website/docs/r/sql_database_instance.html.markdown

@@ -377,9 +377,9 @@ Specifying a network enables private IP.
 At least `ipv4_enabled` must be enabled or a `private_network` must be configured.
 This setting can be updated, but it cannot be removed after it is set.
 
-* `ssl_mode` - (Optional) Specify how SSL connection should be enforced in DB connections.
+* `ssl_mode` - (Optional) Specify how SSL connection should be enforced in DB connections. Supported values are `ALLOW_UNENCRYPTED_AND_ENCRYPTED`, `ENCRYPTED_ONLY`, and `TRUSTED_CLIENT_CERTIFICATE_REQUIRED` (not supported for SQL Server). See [API reference doc](https://cloud.google.com/sql/docs/postgres/admin-api/rest/v1/instances#ipconfiguration) for details.
 
-* `server_ca_mode` - (Optional) Specify how the server certificate's Certificate Authority is hosted. Supported value is `GOOGLE_MANAGED_INTERNAL_CA`.
+* `server_ca_mode` - (Optional) Specify how the server certificate's Certificate Authority is hosted. Supported values are `GOOGLE_MANAGED_INTERNAL_CA` and `GOOGLE_MANAGED_CAS_CA`.
 
 * `allocated_ip_range` - (Optional) The name of the allocated ip range for the private ip CloudSQL instance. For example: "google-managed-services-default". If set, the instance ip will be created in the allocated range. The range name must comply with [RFC 1035](https://datatracker.ietf.org/doc/html/rfc1035). Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])?.