Component: Improve detection of existing language

Avoid looking at text, because it can be part of existing language
object, better to look at ID which indicates whether it has been created
in the database.

weblate/trans/models/component.py

@@ -1865,7 +1865,7 @@ def clean_lang_codes(self, matches):
                 )
                 raise ValidationError({"filemask": message})
             langs.add(code)
-            if "(generated)" not in lang.name:
+            if lang.id:
                 existing_langs.add(lang.code)
 
         # No languages matched our definition