pythongh-134370: Added clarification on instance annotations (python#134387)

Instances of classes cannot have annotations,
however sometimes they will erroneously have the
__annotations__ attribute

Author: AlexKautz

Doc/howto/annotations.rst

@@ -248,4 +248,9 @@ quirks by using :func:`annotationlib.get_annotations` on Python 3.14+ or
 :func:`inspect.get_annotations` on Python 3.10+. On earlier versions of
 Python, you can avoid these bugs by accessing the annotations from the
 class's :attr:`~type.__dict__`
-(e.g., ``cls.__dict__.get('__annotations__', None)``).
+(for example, ``cls.__dict__.get('__annotations__', None)``).
+
+In some versions of Python, instances of classes may have an ``__annotations__``
+attribute. However, this is not supported functionality. If you need the
+annotations of an instance, you can use :func:`type` to access its class
+(for example, ``annotationlib.get_annotations(type(myinstance))`` on Python 3.14+).