Improve empty state for people who can't create a personal project

Problem

The following discussion from !91610 (merged) should be addressed:

  • @cablett started a discussion: (+2 comments)

    I notice we invite someone to create a project under personal projects even if their limit is 0 🤔

    image

    Might be worth a conversation with UX in another issue.

Proposal

Hide the "new project" button in this scenario. Update the heading and explanatory text in the empty state to explain that you're not allowed to create new personal projects.

A related error message from Confusing behaviour when user project limit is ... (#367020 - closed) currently says the following: You are unable to create projects in this namespace. Contact your GitLab administrator. Perhaps some of that could be re-used/expanded on for this issue.

For reference: we have an existing error message on this page for when the user can't create additional personal projects (added in !135666 (merged)). Linking that MR for fuller context

Edited by Amelia Bauerly