ignore code example in comment

nikomatsakis · nikomatsakis · commit 118cad13a5f2 · 2018-07-25T23:57:59.000+03:00
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/values.rs b/src/librustc_mir/borrow_check/nll/region_infer/values.rs
@@ -183,7 +183,7 @@ impl<N: Idx> LivenessValues<N> {
 ///
 /// Example:
 ///
-/// ```rust
+/// ```text
 /// fn foo(x: &'a u32) -> &'a u32 {
 ///    let y: &'0 u32 = x; // let's call this `'0`
 ///    y
