Update Documentation to include requirements for putting aws-exports.js in source control

### 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/dev/CONTRIBUTING.md#bug-reports).
- [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.

### How did you install the Amplify CLI?

_No response_

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

_No response_

### Amplify CLI Version

all up to now (9.1.0)

### What operating system are you using?

all

### Did you make any manual changes to the cloud resources managed by Amplify? Please describe the changes made.

no

### Amplify Categories

Not applicable

### Amplify Commands

Not applicable

### Describe the bug

**tldr;** note in docs for [aws-exports.js](https://docs.amplify.aws/cli/reference/files/#aws-exportsjs) says `Add to version control: NO` but it should explain that it's okay to add inversion control if the developer ensures it gets updated when pushing/pulling the project.

**More context**
In order versions of Amplify, there were some concerns about sensitive information in aws-exports.js going into git:
https://github.com/aws-amplify/amplify-cli/issues/754#issuecomment-456965703
https://github.com/aws-amplify/amplify-js/issues/2495#issuecomment-453282477

These are no longer a concern, so the current reason that it is not in source control is that it's essentially a build artifact that's generated by the CLI based on backend config. A developer could include it in source control _**provided they ensure it gets updated when pushing/pulling the project**_.

The [documentation page](https://docs.amplify.aws/cli/reference/files/#amplify-metajson) should be updated to explain this.

### Expected behavior

Docs explain what is necessary to include aws-exports.js in source control.

### Reproduction steps

Docs page: https://docs.amplify.aws/cli/reference/files/#amplify-metajson

### GraphQL schema(s)

```graphql
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### Project Identifier

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### Log output

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### Additional information

_No response_