add description

clippy_lints/src/needless_if.rs

@@ -7,7 +7,7 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for empty `if` statement with no else branch.
+    /// Checks for empty `if` statements with no else branch.
     ///
     /// ### Why is this bad?
     /// It can be entirely omitted, and often the condition too.