Microsoft.MachineLearningServices/workspaces/connections: authType should accept ApiKey, CustomKeys as possible value

### Resource Type

Microsoft.MachineLearningServices/workspaces/connections

### Api Version

2023-10-01

### Issue Type

Property(s) missing validation for enum values

### Other Notes

Error says:
The property "authType" expected a value of type "'ManagedIdentity' | 'None' | 'PAT' | 'SAS' | 'UsernamePassword'" but the provided value is of type "'ApiKey'". If this is an inaccuracy in the documentation, please report it to the Bicep Team.

However, "ApiKey" is valid and the provisioning succeeds.

See example Bicep here:
https://github.com/Azure-Samples/contoso-chat/pull/33/files#diff-7ef659fc9cf6968e718894d300490b14ea7a52091e7d4bcffae3a5029ac721d4

Same issue for CustomKeys value as well.

### Bicep Repro

_No response_

### Confirm

- [X] I have read the troubleshooting guide and looked for duplicates.

Start by locating the type definition for Microsoft.MachineLearningServices/workspaces/connections at API version 2023-10-01 and inspect the authType allowed values. Confirm that ApiKey and CustomKeys are valid for the resource, then update the relevant validation and run the repository's type-generation or validation checks to verify both values are accepted.

Written by the indexing model from the issue text.