Removal of identity pool in auth update flow does not remove related keys from platform-specific config files.

### 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?

v12.19.0

### Amplify CLI Version

4.44.2

### What operating system are you using?

macOS

### Amplify Categories

auth

### Amplify Commands

update

### Describe the bug

When running `amplify auth update` and updating from a "User Pool + Identity Pool" configuration to "UserPool only", the identity pool is deleted but is still defined in the amplifyconfiguration (native) / aws-exports (js) file.

### Expected behavior

When an identity pool is removed from the auth configuration, the corresponding value should be removed from the configuration file on all platforms.

### Reproduction steps

1. Create an auth resource. For the prompt "Select the authentication/authorization services that you want to use:", select "User Sign-Up, Sign-In, connected with AWS IAM controls (Enables per-user Storage features for
images or other content, Analytics, and more)"
2. Run 'amplify push`.
3. Run 'amplify auth update`. Select the manual flow. For the prompt "Select the authentication/authorization services that you want to use:", select "User Sign-Up & Sign-In only (Best used with a cloud API only)"
4. Run `amplify push`.
5. Check the config file, and note that the identity pool is still defined.

### Log output

N/A

This causes difficult to diagnose [issues](https://github.com/aws-amplify/amplify-flutter/issues/409) when attempting to fetch sessions with the native libraries.