Update compiler/rustc_error_codes/src/error_codes/E0547.md

Co-authored-by: Guillaume Gomez <guillaume1.gomez@gmail.com>

Author: jesusprubio

Diff for: compiler/rustc_error_codes/src/error_codes/E0547.md

@@ -13,7 +13,7 @@ fn _unstable_fn() {}
 fn _unstable_const_fn() {}
 ```
 
-To fix the issue you need to provide the `issue` field.
+To fix this issue, you need to provide the `issue` field. Example:
 
 ```
 #![feature(staged_api)]