Update reference/generics.html with PEP695 type parameter syntax

The typing documentation for generics is somewhat inconsistent in the use of new syntax:

• Generics — typing documentation (https://typing.python.org/en/latest/reference/generics.html) doesn’t include the new syntax class Foo[T] at all

• Generics — typing documentation (https://typing.python.org/en/latest/spec/generics.html) does, and mentions PEP695

Are there any plans on updating reference/generics.html? It is a bit confusing for someone who is using Python 3.12 or newer to see out-of-date information.

从 reference/generics.html 开始，将其中关于泛型的指南与 spec/generics.html 进行比较，尤其关注 PEP 695 的材料和 class Foo[T] 语法。更新参考页面，使其对泛型语法的处理与规范一致，然后检查已渲染的文档，确认示例和措辞相匹配。