[1.14 regression] False positive on abstract Enum subclasses in stubs

While updating typeshed to mypy 1.14 (python/typeshed#13272), we got a few false positive errors on abstract enum classes like fpdf.enums.CoerciveEnum. This is due to the changes from #18068.

Perhaps we can throw the #18068 warning only if the enum class contains at least one attribute annotated with PEP 526 syntax. (cc @hauntsaninja as the author of #18068 and @tungol for the typeshed change.)

まず #18068 の変更とリンク先の typeshed PR の議論を読み、次に fpdf.enums.CoerciveEnum のような抽象 enum クラスで誤検知を再現してください。PEP 526 属性を持たない enum では警告が表示されなくなり、属性を持つ enum では引き続き表示されれば、作業は完了です。