revert using the extension of the blob to determine the syntax highlighting language

nohighlight functionality for a hardcoded set of filenames is kept

app/helpers/blob_helper.rb

 module BlobHelper
   def highlightjs_class(blob_name)
-    if blob_name.include?('.')
-      ext = blob_name.split('.').last
-      return 'language-' + ext
-    else
     if no_highlight_files.include?(blob_name.downcase)
       'no-highlight'
     else
       blob_name.downcase
     end
   end
-  end
 
   def no_highlight_files
     %w(credits changelog copying copyright license authors)