CI: temporarily use rustfmt-nightly on appveyor
CI: temporarily use rustfmt-nightly on appveyor

Undin/intellij-rust,Undin/intellij-rust,anton-okolelov/intellij-rust,Undin/intellij-rust,intellij-rust/intellij-rust,Undin/intellij-rust,anton-okolelov/intellij-rust,Undin/intellij-rust,intellij-rust/intellij-rust,intellij-rust/intellij-rust,anton-okolelov/intellij-rust,intellij-rust/intellij-rust,Undin/intellij-rust,anton-okolelov/intellij-rust,intellij-rust/intellij-rust,intellij-rust/intellij-rust,anton-okolelov/intellij-rust