Remove link to GitHub issues (#4639)

templates/status/404.tmpl

@@ -4,6 +4,5 @@
 	<div class="ui divider"></div>
 	<br>
 	{{if .ShowFooterVersion}}<p>Application Version: {{AppVer}}</p>{{end}}
-	<p>If you think this is an error, please open an issue on <a href="https://github.com/go-gitea/gitea/issues/new">GitHub</a>.</p>
 </div>
 {{template "base/footer" .}}