Pre-flight page links to "Operations" changelog instead of "Enterprise" changelog

## Expected Behavior

The help menu should link to the "Enterprise" changelogs.

## Current Behavior

The help menu links to the "Operations" changelogs.

## Possible Solution

## Steps to Reproduce (for bugs)
1. Start a new Data Node Graylog environment
2. Log in to the pre-flight page
3. Check the "Get Help" menu

## Context

The Operations product was renamed back to Enterprise.

## Your Environment

* Graylog Version: 6.3.x, 7.0.0-rc.2