Remove duplicate classmethod decorator

Author: jimchamp

openlibrary/accounts/model.py

@@ -505,7 +505,6 @@ def get_or_raise(
             raise ValueError('Unable to get Open Library account')
         return account
 
-    @classmethod
     @classmethod
     def get_by_key(cls, key: str) -> 'OpenLibraryAccount | None':
         username = key.split('/')[-1]