Update stdtypes.rst

Co-authored-by: Jelle Zijlstra <[email protected]>

Author: StanFromIreland

Doc/library/stdtypes.rst

@@ -47,7 +47,7 @@ By default, an object is considered true unless its class defines either a
 :meth:`~object.__bool__` method that returns ``False`` or a
 :meth:`~object.__len__` method that
 returns zero, when called with the object. [1]_ If one of the methods raises an
-exception when they are called, the exception is propagated and the object does
+exception when called, the exception is propagated and the object does
 not have a truth value (for example, :data:`NotImplemented`).
 Here are most of the built-in objects considered false: