Remove outdated comments on react-refresh

[cdtkrk]

Related Issue: #9984

EDITED:
See #10784 (comment)

---

Without FAST_REFRESH=false, auto reload on src/index.js does not work.

According to comment, react-refresh should be disabled by default.
This commit changes default value of process.env.FAST_REFRESH.

For testing
$ yarn create-react-app path/to/app.
Edit path/to/app/src/index.js.

[facebook-github-bot]

Hi @kidkkr!

Thank you for your pull request and welcome to our community.

Action Required

In order to merge any pull request (code, docs, etc.), we require contributors to sign our Contributor License Agreement, and we don't seem to have one on file for you.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[petetnt]

Hi @kidkkr,

the FAST_REFRESH support is stable, but the comment has not been updated (it was merged as experimental in #8582 and rolled out as stable in 4.0.0.). The comment should be removed or updated accordingly.

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[cdtkrk]

Okay, @petetnt ! Would you mind if I remove comments in this PR instead?