[Bug][http-client-js]: `@noAuth` at namespace level is not properly supported

### Describe the bug

In todoApp, we have `noAuth` decorated on the namespace Users
```
@useAuth(NoAuth)
namespace Users { }
```
the generated ./src/api/usersClient/usersClientContext.ts file should pass undefined to getClient instead of an undefine credential
```diff
export function createUsersClientContext(
endpoint: string,
options?: UsersClientOptions,): UsersClientContext {
const params: Record = {
endpoint: endpoint
};
const resolvedEndpoint = "{endpoint}".replace(/{([^}]+)}/g, (_, key) =>
key in params ? String(params[key]) : (() => { throw new Error(`Missing parameter: ${key}`); })()
- );;return getClient(resolvedEndpoint,credential,{
+ );;return getClient(resolvedEndpoint,undefined,{
...options,
})
}
```

### Reproduction

https://github.com/allenjzhang/typespec-e2e-demo/tree/main/todoApp/spec

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
- [x] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/Microsoft/typespec/discussions).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.