Update posts/2022-02-24-Rust-1.59.0.md: Fix typo: s/cargo/Cargo/

Co-authored-by: Mark Rousskov <[email protected]>

Author: joshtriplett

posts/2022-02-24-Rust-1.59.0.md

@@ -133,7 +133,7 @@ While this happens very rarely, it can be quite disruptive when a crate used by
 your project has code that will no longer be allowed. In fact, you might not
 notice until your project inexplicably stops building!
 
-cargo now shows you warnings when a dependency will be rejected by a future
+Cargo now shows you warnings when a dependency will be rejected by a future
 version of Rust. After running `cargo build` or `cargo check`, you might see:
 
 ```