Remove unused code in Sequelize's clean_html filter

Also fix it's --> its in code comments

lib/docs/filters/sequelize/clean_html.rb

@@ -18,11 +18,11 @@ module Docs
           # Remove image cards pointing to entries of the manual
           css('.manual-cards').remove
 
-          # Pull the header out of it's container
+          # Pull the header out of its container
           header = at_css('h1')
           header.parent.parent.parent.add_previous_sibling header
         else
-          # Pull the header out of it's container
+          # Pull the header out of its container
           header = at_css('h1')
           header.parent.add_previous_sibling header
         end
@@ -46,11 +46,6 @@ module Docs
           pre['data-language'] = 'typescript' if node['class'] == 'lang-ts'
         end
 
-        # Add syntax highlighting to source files
-        css('pre.raw-source-code').each do |node|
-          node['data-language'] = 'javascript'
-        end
-
         # Return the cleaned-up document
         doc
       end