E0172 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0172.rs

E0172 needs a span_label, updating it from:

error[E0172]: expected a reference to a trait
  --> src/test/compile-fail/E0172.rs:11:13
   |
11 | fn foo(bar: i32+std::fmt::Display) {} //~ ERROR E0172
   |             ^^^

error[E0172]: expected a reference to a trait
  --> src/test/compile-fail/E0172.rs:11:13
   |
11 | fn foo(bar: i32+std::fmt::Display) {} //~ ERROR E0172
   |             ^^^ expected a trait

[Roybie]

taking this one