PR comment / dry-run is processed twice after pushing additional commit after initial PR

## Problem Description

### What is actually happening
If you create a PR it would process as normal. If you then create another commit, the logs show that it is actually listing all the repositories twice. It also results in two new PR comment to be created instead of one.

Because environments are also not processed in dry-run, as part of processing it does a DELETE and because the event is processed twice, a second DELETE appears with a 404 crashing the pod.

### What is the expected behavior
A new commit would just process a single time and create a single new PR comment

### Error output, if available

I can see it is processing twice by seeing that the pages of github repo call are duplicated in the logs

## Context

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

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

#### Version of probot/settings

#### Version of GitHub Enterprise