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.

リテラルの仕様を開き、issue で言及されている不正なパラメーターと実行時のパラメーターに関するセクションを見つけます。規範的な記述を簡潔に保ちながら、根拠と実装詳細のセクションを削除し、その後、レンダリングされた仕様を確認して周辺の内容が引き続き明確であることを確認します。