Changes to not topics not overwritten

## Problem Description
I have configured safe-settings to apply a list of topics to be applied by safe-settings. This work good initially, but when I change the topics manually in the GitHub UI the topics are not applied again by safe-settings.

### What is actually happening
Nothing

### What is the expected behavior
I expect safe-settings to overwrite the list of topics within a few seconds.

### Error output, if available
I didn't see any error message when looking in the console, though it is possible that I missed some since our organization have a lot of activity.

## Context

### Are you using the hosted instance of probot/settings or running your own?
My own instance

### If running your own instance, are you using it with github.com or GitHub Enterprise?

#### Version of probot/settings
Using 028c368fd39eef6f97c24d43115a10eaf41cf2db