E0034 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0034.rs

The E0034 error message needs a span_label, changing it from:

error[E0034]: multiple applicable items in scope
  --> src/test/compile-fail/E0034.rs:25:5
   |
25 |     Test::foo() //~ ERROR E0034
   |     ^^^^^^^^^
   |
note: candidate #1 is defined in an impl of the trait `Trait1` for the type `Test`
  --> src/test/compile-fail/E0034.rs:21:24
   |
21 | impl Trait1 for Test { fn foo() {} }
   |                        ^^^^^^^^^^^
note: candidate #2 is defined in an impl of the trait `Trait2` for the type `Test`
  --> src/test/compile-fail/E0034.rs:22:24
   |
22 | impl Trait2 for Test { fn foo() {} }
   |                        ^^^^^^^^^^^

to:

error[E0034]: multiple applicable items in scope
  --> src/test/compile-fail/E0034.rs:25:5
   |
25 |     Test::foo() //~ ERROR E0034
   |     ^^^^^^^^^ multiple `foo` found
   |
note: candidate #1 is defined in an impl of the trait `Trait1` for the type `Test`
  --> src/test/compile-fail/E0034.rs:21:24
   |
21 | impl Trait1 for Test { fn foo() {} }
   |                        ^^^^^^^^^^^
note: candidate #2 is defined in an impl of the trait `Trait2` for the type `Test`
  --> src/test/compile-fail/E0034.rs:22:24
   |
22 | impl Trait2 for Test { fn foo() {} }
   |                        ^^^^^^^^^^^

Bonus: there may be additional fixes we can do to improve E0034 as well. We could explore underlining the candidates as secondary notes rather than as completely separate notes as one possibility.

[athulappadan]

Let me work on this one.

[sophiajt]

@athulappadan - I haven't heard anything on this from the first person who volunteered, so feel free to take it.