Auto merge of #11168 - weihanglo:remove-Zfeatures, r=Eh2406
Auto merge of #11168 - weihanglo:remove-Zfeatures, r=Eh2406

Remove lingering unstable flag `-Zfeatures`

From [Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/.E2.9C.94.20-Zfeatures):

> Eric Huss: When trying to validate that the feature resolver resolves features in the same way as the dependency resolver. I think it is identical, but there are a lot of complex use cases and flags that aren't covered in the testsuite so I'm not entirely confident. If we ever come across a scenario where it isn't the same, the compare option can be useful to see what differs.

In the future we could pick 61b94c3b0435250a0abb8080867b4af8d7dd88f8 to remove this Z flag.

eminence/cargo,rust-lang/cargo,rust-lang/cargo,eminence/cargo,rust-lang/cargo,eminence/cargo,eminence/cargo,rustyhorde/cargo,rustyhorde/cargo,rust-lang/cargo,rustyhorde/cargo,rustyhorde/cargo