Register model UI bug

### Product Version

- [ ] Amazon SageMaker Studio Classic
- [X] Amazon SageMaker Studio
- [ ] Issue is not related to SageMaker Studio

### Issue Description

When manually registering a model package in a model package group, the field for `Container (ECR URI)`is **not** marked as mandatory. In practice to be able to register a model package, that field is required. The "register" button is grayed out when that field is empty.

### Expected Behavior

N/A

### Observed Behavior

M/A

### Product Category

_No response_

### Feedback Category

_No response_

### Other Details

_No response_

Reproduce manual model package registration in Amazon SageMaker Studio and inspect the Container (ECR URI) field. Done means the field is visibly marked mandatory and the registration control behaves consistently when it is empty; this feedback repository does not mention source files or tests.

Written by the indexing model from the issue text.