Admin Dashboard Project Count Inaccurate
### Summary
Number of projects displayed in the admin dashboard is not updated and inaccurate when new projects are created via the UI or using the API
### Steps to reproduce
Create a new project/s and check the admin dashboard project count which will not take into account the newly created project/s
### What is the current *bug* behavior?
Project count is inaccurate in the admin dashboard after new projects are created due to caching.
### What is the expected *correct* behavior?
Project count should accurately reflect the number of projects on the GitLab instance
### Links
Customer ticket: https://gitlab.zendesk.com/agent/tickets/89493
### Possible fixes
Use `Project.count` to fetch the number of projects in the admin dashboard view instead of [using `Project.cached_count`](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/admin/dashboard/index.html.haml#L13).
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