fix: Correct is_pk_composite method to return False instead of raising an error. False is not a base exception

Author: klagerquist1

flask_appbuilder/models/base.py

@@ -247,7 +247,7 @@ def is_pk(self, col_name):
         return False
 
     def is_pk_composite(self):
-        raise False
+        return False
 
     def is_fk(self, col_name):
         return False