Fix missing_transmute_annotations example

Author: GuillaumeGomez

clippy_lints/src/transmute/mod.rs

@@ -437,8 +437,9 @@ declare_clippy_lint! {
     /// ### Example
     /// ```no_run
     /// # unsafe {
+    /// let mut x: i32 = 0;
     /// // Avoid "naked" calls to `transmute()`!
-    /// let x: i32 = std::mem::transmute([1u16, 2u16]);
+    /// x = std::mem::transmute([1u16, 2u16]);
     ///
     /// // `first_answers` is intended to transmute a slice of bool to a slice of u8.
     /// // But the programmer forgot to index the first element of the outer slice,