Fix build and flake update

[renesat]

Fix build for new nixpkgs:

...
    Checking statix v0.5.8 (/build/source/bin)
error: redundant reference in `println!` argument
  --> bin/src/fix.rs:76:36
   |
76 |                     println!("{}", &src);
   |                                    ^^^^ help: remove the redundant `&`: `src`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_borrows_in_formatting
   = note: `-D clippy::useless-borrows-in-formatting` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::useless_borrows_in_formatting)]`

error: redundant reference in `format!` argument
   --> bin/src/fix.rs:102:54
    |
102 |                 let new_file = format!("{} [fixed]", &path);
    |                                                      ^^^^^ help: remove the redundant `&`: `path`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_borrows_in_formatting

error: redundant reference in `println!` argument
   --> bin/src/fix.rs:115:32
    |
115 |                 println!("{}", &src);
    |                                ^^^^ help: remove the redundant `&`: `src`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_borrows_in_formatting

error: could not compile `statix` (lib) due to 3 previous errors
warning: build failed, waiting for other jobs to finish...

[mightyiam]

Hey. This repo is not maintained. My fork is https://github.com/molybdenumsoftware/statix and I want to merge it back to original:
https://tangled.org/oppi.li/statix/issues/1

[mightyiam]

But, thank you for your contribution. I've just made an addition to the readme to reduce the chances that this occurs again. #168.