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/add-grammar

@@ -84,6 +84,7 @@ if repo_old
   log "Deregistering: #{repo_old}"
   `git submodule deinit #{repo_old}`
   `git rm -rf #{repo_old}`
+  `script/convert-grammars`
 end
 
 log "Registering new submodule: #{repo_new}"
@@ -92,7 +93,11 @@ exit 1 if $?.exitstatus > 0
 `script/convert-grammars --add #{repo_new}`
 
 log "Confirming license"
-`script/licensed --module "#{repo_new}"`
+if repo_old
+  `script/licensed`
+else
+  `script/licensed --module "#{repo_new}"`
+end
 
 log "Updating grammar documentation in vendor/REAEDME.md"
 `bundle exec rake samples`