RFC 2867 is "Add a new #[instruction_set(...)] attribute..."

Author: nikomatsakis

text/0000-isa-attribute.md renamed to text/2867-isa-attribute.md

@@ -1,7 +1,7 @@
 - Feature Name: isa_attribute
 - Start Date: 2020-02-16
-- RFC PR: [rust-lang/rfcs#0000](https://github.com/rust-lang/rfcs/pull/0000)
-- Rust Issue: [rust-lang/rust#0000](https://github.com/rust-lang/rust/issues/0000)
+- RFC PR: [rust-lang/rfcs#2867](https://github.com/rust-lang/rfcs/pull/2867)
+- Rust Issue: [rust-lang/rust#74727](https://github.com/rust-lang/rust/issues/74727)
 
 # Summary
 [summary]: #summary