Improve E0061 long error explanation

Author: GuillaumeGomez

src/librustc_error_codes/error_codes/E0061.md

@@ -1,3 +1,13 @@
+An invalid number of arguments was passed when calling a function.
+
+Erroneous code example:
+
+```compile_fail,E0061
+fn f(u: i32) {}
+
+f(); // error!
+```
+
 The number of arguments passed to a function must match the number of arguments
 specified in the function signature.