Reworded doc topics 'who can view x'

What does this MR do and why?

Reworded doc topics 'who can view x'

In the Manage Epics and Manage Incidents docs, the first bullet point's negative statement is harder to parse and can be reworded to be positive to match the following bullet points.

Solves issue #385291 (closed)

How to set up and validate locally

1. Ensure pipelines pass
2. Look at documentation changes in manage_incidents.md and and manage_epics.md

MR acceptance checklist

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