[bug#54509] bump: make rust-cargo understand rust-edition2021 which rustc already does

[Tobias Geerinckx-Rice]

Hi, 

λ cargo new foo
     Created binary (application) `foo` package
λ cd foo
λ cargo run
λ sed -i 's/2018/2021/' Cargo.toml
λ cargo run
   Compiling foo v0.1.0 (/home/nckx/c/foo)
    Finished dev [unoptimized + debuginfo] target(s) in 1.11s
     Running `target/debug/foo`
Hello, world!
λ echo 'axum = "0.5.4"' >> Cargo.toml
λ cargo run
[...]
Downloaded httpdate v1.0.2
   Compiling foo v0.1.0 (/home/nckx/c/foo)
    Finished dev [unoptimized + debuginfo] target(s) in 54.46s
     Running `target/debug/foo`
Hello, world!

Did you read the entirety of Maxime's reply?  How are you controlling your 
environment?

Kind regards,

T G-R

Sent on the go.  Excuse or enjoy my brevity.