Update copy on Slack product selector page

Context

This work is related to our updates to the Slack landing page (gitlab-com/marketing/digital-experience/buyer-experience#1281 (closed)) for the GitLab + Slack integration.

Problem

The copy on the Slack product selector page will become confusing with the upcoming public Slack integration landing page.

This copy implies that they are setting up the Slack integration for the first time. However, it's possible they've already set up the integration. If they've already set it up, they will go straight to the Slack integration settings.

How the user navigates to this page

The user enters this product selector page when they are setting up the Slack integration from outside of GitLab. For example, from the Slack app directory or the public facing about.gitlab.com page.

Proposal

Text currently	Text should be
Select a GitLab project to link with your Slack workspace.	Select a GitLab project to enable or configure the Slack integration.