updated grammar for 2 questions

[jgeev]

Checklist:

Summary of changes

Updated grammar and code examples for JS arrow function question and nullish coalescing operator.

Screenshots of the updates below

Checklist

• [ X] I have read and followed the contribution guidelines.
• [ X] I have read through the Code of Conduct and agree to abide by the rules.
• [ X] This PR is for one of the available issues and is not a PR for an issue already assigned to someone else.
• [ X] My PR title has a short descriptive name so the maintainers can get an idea of what the PR is about.
• [ X] I have provided a summary of my changes.

#670 and #671

[jdwilkin4]

HI @jgeev !

We will only be reviewing and prioritizing PRs for issues that are free to work on.

Issue No.670, is assignment only.
The first person who replies back to the issue about working on it, will be assigned to that issue.
As for issue No.671, that has already been assigned to the first person who commented on the issue asking to be assigned.

All of the rules for contributing are laid out in the contributing documentation
Please read through that so you know which issues are free to work.

I am going to close this PR but we welcome future contributions on other issues