Unable to clone a repo with private git submodules.

### Before opening, please confirm:

- [X] I have checked to see if my question is addressed in the [FAQ](https://github.com/aws-amplify/amplify-hosting/blob/master/FAQ.md).
- [X] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-hosting/issues?q=is%3Aissue+).
- [X] I have read the guide for [submitting bug reports](https://github.com/aws-amplify/amplify-hosting/blob/master/CONTRIBUTING.md).
- [X] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.
- [X] I have removed any sensitive information from my code snippets and submission.

### App Id

arn:aws:amplify:us-east-1:465512941999:apps/d1zlbbwrkaj7oo

### AWS Region

us-east-1

### Amplify Hosting feature

Git providers

### Frontend framework

React

### Next.js version

13

### Next.js router

App Router

### Describe the bug

When my code has private git submodules, the build step fails. The error is as follows -

```sh
# Unable to update submodules: Error: Command failed: git submodule update
Cloning into '/codebuild/output/src3058105818/src//src/components/common-css-components'...
Host key verification failed.
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@github.com:org/.git' into submodule path '/codebuild/output/src3058105818/src//src/components/common-css-components' failed
Failed to clone 'src/components/common-css-components'. Retry scheduled
Cloning into '/codebuild/output/src3058105818/src//src/components/common-css-components'...
Host key verification failed.
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@github.com:org/.git' into submodule path '/codebuild/output/src3058105818/src/src/components/common-css-components' failed
Failed to clone 'src/components/common-css-components' a second time, aborting
```

### Expected behavior

It should be able to clone the sub module with the connect git app has been provided access to the git sub module repository

### Reproduction steps

1. Add a private git repo to your amplify app
2. push to github to trigger the build job

### Build Settings

_No response_

### Log output

```
# Put your logs below this line

```

### Additional information

_No response_

Start with FAQ.md and CONTRIBUTING.md, then reproduce the Amplify Hosting build from the listed steps with a private Git submodule. Inspect the git submodule update output and the app's Build Settings; done means the build can clone the private submodule without the reported host-key or access error.

Written by the indexing model from the issue text.