E0191 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0191.rs

Error E0191 needs a span_label, updating it from:

error[E0191]: the value of the associated type `Bar` (from the trait `Trait`) must be specified
  --> src/test/compile-fail/E0191.rs:15:12
   |
15 | type Foo = Trait; //~ ERROR E0191
   |            ^^^^^

To:

error[E0191]: the value of the associated type `Bar` (from the trait `Trait`) must be specified
  --> src/test/compile-fail/E0191.rs:15:12
   |
15 | type Foo = Trait; //~ ERROR E0191
   |            ^^^^^ missing associated type `Bar` value

[munyari]

I'll take this