re-mark the never docs as unstable

QuietMisdreavus · QuietMisdreavus · commit dda7e0dec6d3 · 2018-09-13T17:31:56.000-05:00
diff --git a/src/libstd/primitive_docs.rs b/src/libstd/primitive_docs.rs
@@ -250,6 +250,7 @@ mod prim_bool { }
 /// [`Default`]: default/trait.Default.html
 /// [`default()`]: default/trait.Default.html#tymethod.default
 ///
+#[unstable(feature = "never_type", issue = "35121")]
 mod prim_never { }
 
 #[doc(primitive = "char")]
