Add RwLock lint pass and remove unused explicit write test

Author: Tunglies

clippy_lints/src/lib.rs

@@ -849,6 +849,7 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
         Box::new(|_| Box::new(toplevel_ref_arg::ToplevelRefArg)),
         Box::new(|_| Box::new(volatile_composites::VolatileComposites)),
         Box::new(|_| Box::<replace_box::ReplaceBox>::default()),
+        Box::new(|_| Box::new(rwlock_atomic::RwLock)),
         // add late passes here, used by `cargo dev new_lint`
     ];
     store.late_passes.extend(late_lints);