Remove login button from gone page when already logged in

Fixes #414

app/templates/packages/gone.html

@@ -39,9 +39,13 @@
 	{% endif %}
 	<p>
 		{{ _("Please check back again later.") }}
+		{% if not current_user.is_authenticated %}
 			{{ _("Or, if you're the author, log in to see more information.") }}
+		{% endif %}
 	</p>
+	{% if not current_user.is_authenticated %}
 		<p>
 			<a href="{{ url_for('users.login') }}" class="btn btn-primary">{{ _("Login") }}</a>
 		</p>
+	{% endif %}
 {% endblock %}