add space in open graph title

src/plainui/jinja2/plainui/components/open_graph.html.j2

 {% macro headers(title, type="website", site_name=None, image=None, description=None) -%}
   {% if site_name %}<meta property="og:site_name" content="{{ site_name }}" />{% endif %}
   <meta property="og:title"
-        content="{%- if site_name -%}{{ site_name }}: {%- endif -%}{{ title }}" />
+        content="{%- if site_name -%}{{ site_name }}: {% endif -%}{{ title }}" />
   <meta property="og:type" content="{{ type }}" />
   {% if image %}
     <meta property="og:image" content="{{ image.url }}" />