Fix documentation of eval_order_dependence

Author: chansuke

clippy_lints/src/eval_order_dependence.rs

@@ -15,8 +15,8 @@ declare_clippy_lint! {
     /// order of sub-expressions.
     ///
     /// ### Why is this bad?
-    /// It is often confusing to read. In addition, the
-    /// sub-expression evaluation order for Rust is not well documented.
+    /// It is often confusing to read. As described [here](https://doc.rust-lang.org/reference/expressions.html?highlight=subexpression#evaluation-order-of-operands),
+    /// the operands of these expressions are evaluated before applying the effects of the expression.
     ///
     /// ### Known problems
     /// Code which intentionally depends on the evaluation