Remove some dead or leftover code related to rustc-intrinsic abi removal

compiler/rustc_error_codes/src/error_codes/E0622.md

@@ -1,8 +1,10 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 An intrinsic was declared without being a function.
 
 Erroneous code example:
 
-```compile_fail,E0622
+```no_run
 #![feature(intrinsics)]
 #![allow(internal_features)]