Update Rust toolchain to 1.89 (#15157)

## Summary

Bumps Rust toolchain to 1.89, but not the MSRV.

Lifetime changes is related to a new lint rule explained in
https://blog.rust-lang.org/2025/08/07/Rust-1.89.0/#mismatched-lifetime-syntaxes-lint

## Test Plan

Existing Tests

crates/uv-git/src/resolver.rs

@@ -45,7 +45,7 @@ impl GitResolver {
     }
 
     /// Returns the [`GitOid`] for the given [`RepositoryReference`], if it exists.
-    fn get(&self, reference: &RepositoryReference) -> Option<Ref<RepositoryReference, GitOid>> {
+    fn get(&self, reference: &RepositoryReference) -> Option<Ref<'_, RepositoryReference, GitOid>> {
         self.0.get(reference)
     }