Update comments

Author: doctorn

src/librustc_error_codes/error_codes/E0583.md

@@ -2,7 +2,7 @@ A file wasn't found for an out-of-line module.
 
 Erroneous code example:
 
-```ignore (compile_fail not working here; see Issue #43707)
+```compile_fail,E0583
 mod file_that_doesnt_exist; // error: file not found for module
 
 fn main() {}

src/librustc_error_codes/error_codes/E0761.md

@@ -14,7 +14,7 @@ fn foo() {}
 fn foo() {}
 ```
 
-```ignore (compile_fail not working here; see Issue #43707)
+```ignore (multiple source files required for compile_fail)
 mod ambiguous_module; // error: file for module `ambiguous_module`
                       // found at both ambiguous_module.rs and
                       // ambiguous_module.rs/mod.rs