deps: bump rustc-ap crates to v683

[calebcartwright]

Resolves #4355

[calebcartwright]

AppVeyor failures are spurious

Build started
git clone -q https://github.com/rust-lang/rustfmt.git C:\projects\rustfmt
git fetch -q origin +refs/pull/4469/merge:
git checkout -qf FETCH_HEAD
Running Install scripts
appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
Downloading rustup-init.exe (6,663,680 bytes)...100%
if "%TARGET%" == "i686-pc-windows-gnu" set PATH=%PATH%;C:\msys64\mingw32\bin
if "%TARGET%" == "x86_64-pc-windows-gnu" set PATH=%PATH%;C:\msys64\mingw64\bin
set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
rustup-init.exe --default-host %TARGET% --default-toolchain %CHANNEL% --profile minimal -y
info: profile set to 'minimal'
info: setting default host triple to i686-pc-windows-gnu
info: syncing channel updates for 'nightly-i686-pc-windows-gnu'
info: update not yet available, sorry! try again later
info: default toolchain set to 'nightly'
  nightly unchanged - (toolchain not installed)
Rust is installed now. Great!
To get started you need Cargo's bin directory (%USERPROFILE%\.cargo\bin) in 
your PATH
environment variable. Future applications will automatically have the
correct environment, but you may need to restart your current shell.
rustc -Vv
info: syncing channel updates for 'nightly-i686-pc-windows-gnu'
info: update not yet available, sorry! try again later
error: toolchain 'nightly-i686-pc-windows-gnu' is not installed
Command exited with code 1