Update tracking issue for extern_crate_self

Author: petrochenkov

src/libsyntax/feature_gate.rs

@@ -494,7 +494,7 @@ declare_features! (
     (active, lint_reasons, "1.31.0", Some(54503), None),
 
     // `extern crate self as foo;` puts local crate root into extern prelude under name `foo`.
-    (active, extern_crate_self, "1.31.0", Some(54658), None),
+    (active, extern_crate_self, "1.31.0", Some(56409), None),
 );
 
 declare_features! (

src/test/ui/feature-gates/feature-gate-extern_crate_self.stderr

@@ -1,4 +1,4 @@
-error[E0658]: `extern crate self` is unstable (see issue #54658)
+error[E0658]: `extern crate self` is unstable (see issue #56409)
   --> $DIR/feature-gate-extern_crate_self.rs:1:1
    |
 LL | extern crate self as foo; //~ ERROR `extern crate self` is unstable