Fix add-grammar and convert-grammars (#3354)

* Skip removed grammar submodule

* Clean up old grammar from grammars and grammars.yml

* Clean up unused grammar license

Run `script/licensed`.
This was missing change in 12f9295 of #3350.

* Clean up license files when we replace grammar

Update license files by running `script/licensed`.
Since we replace grammar, the old grammar license must be removed
and new grammar license must be added.

script/convert-grammars

@@ -174,6 +174,7 @@ end
 def load_grammars(tmp_dir, source, all_scopes)
   is_url = source.start_with?("http:", "https:")
   return [] if is_url && !$options[:remote]
+  return [] if !is_url && !File.exist?(source)
 
   p = if !is_url
         if File.directory?(source)