nix: rust-1.64

rust-1.64 was announced[0].

Update the nix sources to pick up the latest stable. This update
requires some fixes suggested by clippy.

[0]: https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>

git-ref-format/core/src/lit.rs

@@ -21,7 +21,7 @@ pub trait Lit: Sized + sealed::Sealed {
 
     #[inline]
     fn from_component(c: &name::Component) -> Option<Self> {
-        (c.as_ref() == Self::NAME).then(|| Self::SELF)
+        (c.as_ref() == Self::NAME).then_some(Self::SELF)
     }
 }