Fix typo in object-curly-newline.md

[danny-andrews]

It looks like the curly braces got turned into square brackets between the incorrect and correct code examples.

What is the purpose of this pull request? (put an "X" next to item)

[X] Documentation update

What changes did you make? (Give an overview)

See commit message.

[mention-bot]

@danny-andrews, thanks for your PR! By analyzing the history of the files in this pull request, we identified @mysticatea, @scriptdaemon and @alberto to be potential reviewers.

[eslintbot]

Thanks for the pull request, @danny-andrews! I took a look to make sure it's ready for merging and found some changes are needed:

• The commit summary needs to begin with a tag (such as Fix: or Update:). Please check out our guide for how to properly format your commit summary and update it on this pull request.

Can you please update the pull request to address these?

(More information can be found in our pull request guide.)

[gyandeeps]

Make sure to update the commit message

[not-an-aardvark]

LGTM. Thanks!