add tracking issue

Author: nikomatsakis

text/2396-target-feature-1.1.md

@@ -1,7 +1,7 @@
 - Feature Name: `#[target_feature]` 1.1
 - Start Date: 2018-04-06
 - RFC PR: [rust-lang/rust#2396](https://github.com/rust-lang/rfcs/pull/2396)
-- Rust Issue: (leave this empty)
+- Rust Issue: [rust-lang/rust#69098](https://github.com/rust-lang/rust/issues/69098)
 
 # Summary
 [summary]: #summary