Hide "Suggest wiki improvement" button on "Wiki" page from Auditors

Summary

"Suggest wiki improvement" on "Wiki" page should not be shown to Auditors as they have read-only permissions.

Steps to reproduce

1. Create a project
2. Log-in as an Auditor
3. Navigate to "Project" -> "Wiki"

What is the current bug behavior?

"Suggest wiki improvement" button is shown to Auditors but returns a 404 if clicked

What is the expected correct behavior?

"Suggest wiki improvement" should not be shown to Auditors

Relevant logs and/or screenshots

Possible fixes

Add show_new_issue_link?(@project) check to app/views/shared/empty_states/_wikis.html.haml#L28