Auto merge of #16277 - servo:1.16, r=Manishearth
Auto merge of #16277 - servo:1.16, r=Manishearth

Update stable Rust version to 1.16.0

Firefox did this in https://bugzilla.mozilla.org/show_bug.cgi?id=1351031

Together with https://github.com/servo/servo/pull/16276, this gets us support for `./mach cargo-geckolib check`.

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