Fixed issue with manifest.json route

• Fixed:
- issue with manifest.json route, now returning hardcoded json successfully

app/serializers/manifest_serializer.rb

@@ -1,65 +0,0 @@
-# frozen_string_literal: true
-
-class ManifestSerializer < ActiveModel::Serializer
-  include RoutingHelper
-  include ActionView::Helpers::TextHelper
-
-  attributes :name, :short_name, :description,
-             :icons, :theme_color, :background_color,
-             :display, :start_url, :scope,
-             :share_target
-
-  def name
-    'Gab Social'
-  end
-
-  def short_name
-    'Gab Social'
-  end
-
-  def description
-    'Gab is a social network that champions free speech, individual liberty and the free flow of information online. All are welcome.'
-  end
-
-  def icons
-    [
-      {
-        src: '/android-chrome-192x192.png',
-        sizes: '192x192',
-        type: 'image/png',
-      },
-    ]
-  end
-
-  def theme_color
-    '#21D07B'
-  end
-
-  def background_color
-    '#191b22'
-  end
-
-  def display
-    'standalone'
-  end
-
-  def start_url
-    '/home'
-  end
-
-  def scope
-    root_url
-  end
-
-  def share_target
-    {
-      url_template: 'share?title={title}&text={text}&url={url}',
-      action: 'share',
-      params: {
-        title: 'title',
-        text: 'text',
-        url: 'url',
-      },
-    }
-  end
-end