Link out to the RFC

Author: epage

text/3857-cfg-version.md

@@ -1,6 +1,6 @@
 - Feature Name: `cfg_version`
 - Start Date: 2025-09-13
-- RFC PR: [rust-lang/rfcs#0000](https://github.com/rust-lang/rfcs/pull/0000)
+- RFC PR: [rust-lang/rfcs#3857](https://github.com/rust-lang/rfcs/pull/3857)
 - Rust Issue: [rust-lang/rust#64796](https://github.com/rust-lang/rust/issues/64796)
 
 # Summary