E0403 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0403.rs

E0403 needs a span_label, updating it from:

error[E0403]: the name `T` is already used for a type parameter in this type parameter list
  --> src/test/compile-fail/E0403.rs:11:11
   |
11 | fn foo<T, T>(s: T, u: T) {} //~ ERROR E0403
   |           ^

To:

error[E0403]: the name `T` is already used for a type parameter in this type parameter list
  --> src/test/compile-fail/E0403.rs:11:11
   |
11 | fn foo<T, T>(s: T, u: T) {} //~ ERROR E0403
   |           ^ already used

Bonus: Add a span_label for the conflicting first use:

error[E0403]: the name `T` is already used for a type parameter in this type parameter list
  --> src/test/compile-fail/E0403.rs:11:11
   |
11 | fn foo<T, T>(s: T, u: T) {} //~ ERROR E0403
   |        -  ^ already used
   |        |
   |        first use of `T`