Adding a required "simple" data type return type on a graphql query makes codegen produce invalid typescript code

### Before opening, please confirm:

- [X] I have installed the latest version of the Amplify CLI (see above), and confirmed that the issue still persists.
- [X] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-cli/issues?q=is%3Aissue+).
- [X] I have read the guide for [submitting bug reports](https://github.com/aws-amplify/amplify-cli/blob/master/CONTRIBUTING.md#bug-reports).
- [X] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.

### How did you install the Amplify CLI?

npm

### If applicable, what version of Node.js are you using?

14.15.3

### Amplify CLI Version

7.6.5

### What operating system are you using?

mac

### Amplify Categories

api

### Amplify Commands

codegen

### Describe the bug

Try this graphql query

```
updateDate(
newDate: AWSDateTime!
): AWSDateTime!
@function(name: "MyGraphQLResolverFn-${env}")
```

The typescript codegen code produced will be:

```
async UpdateDate(
newDate: string
): Promise
```

But the type ```UpdateDateQuery``` won't be defined in API.service.ts

If I remove the exclamation mark in the AWSDateTime return type, then return type is accurately Promise. So why can't I get it to return ```Promise```?

### Expected behavior

generated code should return ```Promise```

### Reproduction steps

See above description

### GraphQL schema(s)

See above

### Log output

```
# Put your logs below this line

```

### Additional information

_No response_