Auto merge of #11001 - Muscraft:fix-unstable-docs, r=weihanglo

remove missed reference to workspace inheritance in unstable.md

Currently on the nightly docs, workspace inheritance is [under the  stable table](https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#workspace-inheritance-1)  and the [unstable table](https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#workspace-inheritance). It looks like I forgot to remove it from the unstable table when working on stabilization.

I am not sure if it is worth a beta backport but I will happily open a PR for it if needed.