chore: use workspace rust version in backend-interface crate (#2896)

tooling/backend_interface/Cargo.toml

@@ -4,7 +4,7 @@ description = "The definition of the backend CLI interface which Nargo uses for
 version = "0.11.0"
 authors.workspace = true
 edition.workspace = true
-rust-version = "1.66"
+rust-version.workspace = true
 license.workspace = true
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html