set RFC number

Author: RalfJung

text/0000-maybe-dangling.md renamed to text/3336-maybe-dangling.md

@@ -2,7 +2,7 @@
 
 - Feature Name: `maybe_dangling`
 - Start Date: 2022-09-30
-- RFC PR: [rust-lang/rfcs#0000](https://github.com/rust-lang/rfcs/pull/0000)
+- RFC PR: [rust-lang/rfcs#3336](https://github.com/rust-lang/rfcs/pull/3336)
 - Rust Issue: [rust-lang/rust#0000](https://github.com/rust-lang/rust/issues/0000)
 
 # Summary