Fix UnboundLocalError in core.py

Remove redundant 'import gpodder' inside Core.__init__() that was
shadowing the global gpodder module, causing UnboundLocalError when
accessing gpodder.home and gpodder.database_file.

Author: Cut5nake

src/gpodder/core.py

@@ -41,7 +41,6 @@ def __init__(self,
             self.db = dbfactory.create_database(self.config)
         else:
             # For backwards compatibility and testing
-            import gpodder
             self.db = database_class(gpodder.database_file)
 
         self.model = model_class(self.db)