Offline rustdoc html missing favicon.

[eval-exec]

Location (URL)

file:///home/exec/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/share/doc/rust/html/index.html

Summary

1. I execute:

❯ rustup doc
Opening docs in your browser

2. then switch to browser, I can notice that the offline html page have no favicon.
   file:///home/exec/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/share/doc/rust/html/index.html

I think we should set the offline html doc's favicon to https://github.com/rust-lang/rust/blob/master/src/librustdoc/html/static/images/favicon.svg

[GuillaumeGomez]

Fixed in #146170.