chore: remove old filters, hardcoded types, old post status from view

src/includes/base.liquid

@@ -142,7 +142,7 @@
               "inLanguage": "{{ globals.locale }}",
               "publisher": { "@type": "{{ globals.site_type }}", "name": "{{ globals.author }}", "url": "{{ globals.url }}" },
               "author": { "@type": "Person", "name": "{{ globals.author }}" },
-              "datePublished": "{{ page.date | isoDateOnly: '.' }}"
+              "datePublished": "{{ page.date | date: "%Y.%m.%d" }}"
             }
           {%- endif -%}
         ]

src/includes/partials/blocks/banners/old-post.liquid

@@ -1,4 +1,3 @@
-{%- assign isOldPost = date | oldPost -%}
 {%- if isOldPost -%}
   <div class="banner old-post">
     <p>{% tablericon "clock-x" %}This post is over 3 years old. I've probably changed my mind since it was written and it <em>could</em> be out of date.</p>