remove duplicated columns from rustc_error_code::error_codes!

Author: cyrgani

compiler/rustc_error_codes/src/error_codes/E0773.md

@@ -1,4 +1,4 @@
-#### this error code is no longer emitted by the compiler.
+#### Note: this error code is no longer emitted by the compiler.
 
 This was triggered when multiple macro definitions used the same
 `#[rustc_builtin_macro(..)]`. This is no longer an error.