Remove unused project macros file

The only macro was render_secondary_navigation, which is in the _navigation.pug
template together with the other Blender Cloud navigation macros.

src/templates/projects/_macros.pug

@@ -1,58 +0,0 @@
-include ../mixins/components
-
-| {% macro render_secondary_navigation(project, navigation_links, title) %}
-
-| {% if project.category == 'course' %}
-| {% set category_url = url_for('cloud.courses') %}
-| {% elif project.category == 'workshop' %}
-| {% set category_url = url_for('cloud.workshops') %}
-| {% elif project.category == 'film' %}
-| {% set category_url = url_for('cloud.open_projects') %}
-| {% else %}
-| {% set category_url = url_for('main.homepage') %}
-| {% endif %}
-
-+nav-secondary()
-	| {% if project.url != 'blender-cloud' %}
-	| {% if not project.is_private %}
-	li.text-capitalize
-		a.nav-link.text-muted.px-0(href="{{ category_url }}")
-			| {% if project.category == 'film' %}
-			span Open Projects
-			| {% elif project.category == 'assets' %}
-			span Libraries
-			| {% else %}
-			span {{ project.category }}
-			| {% endif %}
-	li.px-1
-		i.pi-angle-right
-	| {% endif %}
-
-	+nav-secondary-link(
-		class="px-1 font-weight-bold{% if title == 'landing' %} active{% endif %}",
-		href="{{url_for('projects.view', project_url=project.url, _external=True)}}")
-		span {{ project.name }}
-	| {% endif %}
-
-	| {% for link in navigation_links %}
-	+nav-secondary-link(
-		href="{{ link['url'] }}",
-		class="{% if link['slug'] == title %}active{% endif %}")
-		span {{ link['label'] }}
-	| {% endfor %}
-
-	| {% if project.nodes_featured %}
-	| {# In some cases featured_nodes might might be embedded #}
-	| {% if '_id' in project.nodes_featured[0] %}
-	| {% set featured_node_id=project.nodes_featured[0]._id %}
-	| {% else %}
-	| {% set featured_node_id=project.nodes_featured[0] %}
-	| {% endif %}
-	+nav-secondary-link(
-			href="{{ url_for('projects.view_node', project_url=project.url, node_id=featured_node_id) }}",
-			title="Explore {{ project.name }}",
-			class="{% if title == 'project' %}active{% endif %}")
-			span Browse
-	| {% endif %}
-
-| {% endmacro %}