Spec: PEP leftovers in the spec for literals

There are some sections in the spec for literals that made sense as a rationale or look into the future in the PEP, but should be removed in the spec for conciseness, clarity, and consistency:

• An (incomplete) list of illegal parameters for Literal. Since this immediately succeeds a positive, exclusive list of what parameters are allowed, this is just fluff and I believe the whole section should just be removed.
• The next section is titled "Parameters at runtime" and details implementation details for Literal. These seem unnecessary for the typing spec and are in danger of getting desynched with the actual implementation.

打开字面量规范，找到 issue 中提到的非法参数和运行时参数相关章节。删除理由和实现细节章节，同时保持规范性描述简洁，然后检查渲染后的规范，以确认周围内容仍然清晰。