Always update rust when building libavif on Windows

[radarhere]

Recently in the libavif PR, an error occurred when building rav1e in Windows wheels. I reported it at AOMediaCodec/libavif#2703, and the suggestion was to install a Rust toolchain - fdintino#32

I opted for a simpler fix, rustup update - fdintino#33

I noticed the same problem happening in the non-wheels Windows jobs, but a new runner image fixed the problem.

#8851 (comment) has now reported a problem building rav1e in the Windows jobs. Those jobs have, for some reason, decided to suddenly use a runner image two weeks old.

Running the jobs again allows them to pass, but I offer this PR as a more proactive measure if you would like one - running rustup update in all the Windows builds.

[hugovk]

Thanks! Good to know we can restart it and hopefully get the newer runner.

I'll go ahead with the release without merging it to save a bunch of CI time, but we can merge it afterwards if we see it pop up again.

[wiredfool]

Does this mean that we have rust available across all the platforms now?

[radarhere]

Not quite. Cygwin and the Docker images don't have rust, but they also don't have libavif support at the moment. I don't think MinGW has rust, but I might just be missing some MinGW nuance.

[kmilos]

I don't think MinGW has rust, but I might just be missing some MinGW nuance.

MSYS2 distribution of MinGW has: https://packages.msys2.org/base/mingw-w64-rust

Also, libavif and rav1e are usually up to date there, one would rarely need to build them (static libs also included).