Exclude improperly named entries from ISO-639-3

Fixes #1851909 [Some strange languages is shown in the list](https://bugs.launchpad.net/calibre/+bug/1851909)

setup/translations.py

@@ -813,6 +813,8 @@ def run(self, opts):
             name = x.get('name')
             if name:
                 name = unicode_type(name)
+            if not name or name[0] in '!~=/\'"':
+                continue
 
             if two is not None:
                 by_2[two] = name