Contrib docs: clippy all-targets (#7263)

CONTRIBUTING.md

@@ -86,7 +86,7 @@ Please also make sure that the following commands pass if you have changed the c
 cargo check --all
 cargo test --all --all-features
 cargo +nightly fmt -- --check
-cargo +nightly clippy --all --all-features -- -D warnings
+cargo +nightly clippy --all --all-targets --all-features -- -D warnings
 ```
 
 If you are working in VSCode, we recommend you install the [rust-analyzer](https://rust-analyzer.github.io/) extension, and use the following VSCode user settings: