E0124 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0124.rs

Error E0124 needs a span_label and a span_note replaced with a span_label, updating it from:

error[E0124]: field `field1` is already declared
  --> src/test/compile-fail/E0124.rs:13:5
   |
13 |     field1: i32, //~ ERROR E0124
   |     ^^^^^^^^^^^
   |
note: previously declared here
  --> src/test/compile-fail/E0124.rs:12:5
   |
12 |     field1: i32,
   |     ^^^^^^^^^^^

To:

error[E0124]: field `field1` is already declared
  --> src/test/compile-fail/E0124.rs:13:5
   |
12 |     field1: i32,
   |     ----------- first declared here
13 |     field1: i32, //~ ERROR E0124
   |     ^^^^^^^^^^^ field already declared

[sciyoshi]

Error message updated in #35318.