Refactoring: add braces to arrow function

[DanielRosenwasser]

Insightfully suggested in #23299 by @zaaack:

+1. Add braces is very useful, too.

Then substantiated further by @zuozijian3720:

+1. Add braces is very useful, too.

[oliverjanik]

And remove?

[oliverjanik]

This is awesome!